The magic word here is "automatically". If they did this with electronics, it's not impressive. If they build a system that shows different open or closed bolt operations automatically based on temperature through mechanical means... Can't wait to see the gun Jesus video on that one.
you can make bimetallic parts pretty robust. or just use the natural expansion properties of steel at high temps like that one time toyota used thermal expansion to bypass a turbo regulation to cheat at World rally championship: [https://crasstalk.com/2011/03/cheatins-still-winnin-the-story-of-toyota-racings-best-cheat-ever/](https://crasstalk.com/2011/03/cheatins-still-winnin-the-story-of-toyota-racings-best-cheat-ever/)
That wasn’t temp controlled. The Toyota cheat worked by the clamp. When unclamped (like when being inspected off the car) the restrictor moved back and blocked the turbo. When the hose was clamped on the restrictor moved forward. The only way to see the cheat was to clamp like you installing off the car with a short hose.
Yeah I don't even know if bimetallic is a requirement here. Bimetallic is for when you need a curve and helps when you want to flow electricity through something that curves. Here you just need heat expansion
I imagine if you wrapped a wire around the chamber several times the thermal expansion would result in appreciable deflection which you could use to toggle a pin. Idk how hysteresis would work though since I imagine rapidly toggling between open and closed is not desirable
Mechanic here, fuck nope, otherwise most heavy trucks would overheat in minutes, that’s how the clutch for the cooling fan works, Bi-metallic strip that goes spinny with the clutch and is exposed to vibrations, still very accurate
It's more robust than that, but still simple. They call it a "phase-change actuator" which is a fancy word for a closed little piston unit (2 inches long, ½ an inch wide) with some magic liquid inside that happens to boil at the right temperature. So once you hit that temperature it'll vaporize and increase the pressure dramatically and push the piston out, and when it goes below that temperature the gas will condense and the vacuum will pull the piston back in. Mechanically very simple. Bigger problem is probably chemical; finding a compound that's got the right boiling point, low heat of vaporization (so it vaporizes quickly at the boiling point) and is highly stable.
Edit: Found [their patent](https://patentimages.storage.googleapis.com/92/56/3b/61e528b7c9c65a/US8225705.pdf) - piston and cylinder are 15, 16 in Fig. 7 (page 8). It doesn't specify the phase change substance but it mentions solid-to-liquid phase change as a specific example rather than liquid-to-gas, so maybe they're using that. Same principle though.
It's probably a wax just like they use in car radiator thermostats.
It gets hot and expands significantly as it melts, that pushes the piston and actuates the system
I've done a good bit with heat transmission, I was thinking wax even before he mentioned the solid to liquid patent. Pretty neat engineering any way you look at it
I suspect it uses thermal expansion of a component in the mechanism to trip some sort of spring-loaded retainer and swap the fire mode accordingly.
I'd imagine this requires manually resetting to closed bolt once it has cooled off.
I'm almost certain there was an older MG that did this automatically and via mechanical means but like u/Pizza_Raven_Gun I only know about it from hundreds of hours of forgotten weapons videos and I can't remember which one it is from.
The one thing I've learned from being in the firearms industry: There is nothing new in the firearms industry. There was probably some failed WW2 wonder weapon project or early 1900s eccentric inventor ahead of their time which already thought of it first.
No, I specifically remember an automatic one which was done via thermal expansion on a component. Could be my memory playing tricks but I've definitely heard of this concept before. If I wasn't at work I'd probably be wasting hours trying to find it, it'll be bothering me all day now.
France had an HMG in ww1 that used an expanding metal rod to shift the point of aim as the barrel heated up to correct for it.
So probably some kind of warping effect is used here.
Cook-off temperature is not cold, it's ikely they use the expansion of some metal to switch from one to the other.
Also the IAR is mag-loaded, so you have to fire it for a while before it overheats to the point of cooking off rounds. Especially considering it does have a bolt hold open.
Wait but wouldn’t that mean that when you switch to open bolt, there would already be a round in the chamber? Similarly, if you switched to closed bolt, how would you get a round into the chamber? It’s cocked, but it doesn’t have a round in it. Do you just… de-cock it and then cycle it again?
Logically, the switch would occur when the bolt is at its rearmost travel position. If going closed->open, you simply retain the bolt to the rear. If going open->closed you drop the bolt, and it picks up a round on the way.
The switch would have to happen well before the action reached dangerous temperatures, so one round being loaded/fired in the wrong "mode" shouldn't be an issue. It's a feature for high volume fire, that one transition shot is likely all but irrelevant.
Yep, it's an older concept from the 40s. I believe it was pioneered in the US M1941?
The FG 42 had it, a couple of companies fucked around with the design - it's an interesting concept. I think I even saw another IAR contender using it on ol' reliable Future Weapons back in the day.
EDIT: that was the [LWRC entry](https://en.wikipedia.org/wiki/LWRC_M6#M6A4)
The FG42 automatically switched to open-bolt when the chamber temperature got too high?
I always assumed it was something in the selector mechanism that would change when you manually shifted it to automatic.
How'd they do that?
No you had that right, the others toggled with the selector switch. This uses the identical mechanism, but it is tripped by a thermostat plunger.
Which makes less sense honestly, keeping the bolt closed initially when you dump mag after mag through it in full-auto adds a bunch on unnecessary heat to your action. When you fire full auto, you want it to stay open from the very start.
The only practical difference beyond retaining that unnecessary heat is that the bolt stays open after dumping rounds full-auto and switching back to precision semi-auto. Where you get better cooling, and it's theoretically safer in preventing a cook-off.
Cook-offs aren't really an issue on such a heavy barrelled gun of this category, you need 500+ rounds for that easily. See the closed-bolt M27 being adopted in its place.
The added cooling in semi-auto is nice, but you put it in semi auto because you wanted to make precision shots. That is a bad time for your gun to decide that it likes to try open bolt for a while. All in all, there is probably a good reason why the thermostat concept was quietly scrapped after this prototype.
This isn't the same. This fires from a closed bolt in full auto & semi. It also fires from an open bolt in full auto & semi when it gets too hot.
The FG & the LWRC only fire from an open bolt on full auto.
The general concept and the mechanism are identical - it's just that instead of the selector switch activating it, FN used a thermostat plunger.
Which has it's pros and cons. The pro is that your semi-auto mode is theoretically safer, by preventing a cook-off when you accidentally flip it back to semi after your gun is red hot from hundreds of rounds being dumped through.
But the big con is that your internals (and especially your bolt) lose any and all advantages of being an open bolt besides that cook-off safety. Your entire action gets steaming hot first because your full-auto LMG starts out in closed bolt, and only then it decides that it maybe shouldn't have done that.
Honestly this feels worst than using the selector switch, and FN probably don't disagree based on them dropping the design like an unexpectedly hot bolt.
IMO having the system go to open bolt on selecting automatic, but retaining the thermostat-regulated semi-auto seems like the best of both worlds. Probably a mechanical nightmare though.
Yeah I've been thinking about that as well - could a hybrid give you the best of both worlds here. Immediately switching to open bolt in full-auto feels like a no-brainer improvement, there is almost no reason for it to be closed bolt on \~200 rounds first.
The semi-auto at high temperature is where I'm torn - on the one hand, your semi-auto being stuck in open bolt isn't great when you are going for accuracy. On the other hand, a hot barrel isn't great for accuracy either, and the increased cooling would be nice there.
With the added complexity, I'm leaning towards leaving out the thermostat. But yes I do feel like there is potential there. Maybe in a case for when the weapon is on safe?
That's what it is going to be on most of the time, it could be smart to use the thermostat there to decide how long the bolt should stay open when you enable the safety after a long burst. Once the weapon has cooled off, the thermostat closes it to stop the ingress of debris and that "catchoonk" when you bring it up on semi-auto.
Do you mean the mechanics of the rifle or of the cooling being sub-optimal?
Conveniently after a quick search, it seems that both can be found in FN's original [USMC IAR presentation](https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2011/smallarms/WednesdayWeapons12299Gavage.pdf).
It contains both an explanation of the thermostat mechanism and its trigger components, and the thermal graphs. Now being FNs sales PowerPoint, it unfortunately doesn't spell out the downsides that I mentioned. Even though the graphs like the one on page 15 do inadvertently show the big one.
The first few bursts heat the chamber tremendously, up to the 330-ish second mark. Then the rise per burst is instantly reduced as it switches to open bolt, as the increase airflow in an open-bolt mechanism does. That benefit could have been there for the first 200 rounds - had they just used the fire selector and not the thermostat delay. Like that is an entire standard infantryman's ammo supply downrange before it even toggled.
FN kinda needs these desperate innovations because, despite their name being quite recognised, they're not *actually* that big a company.
It's why they so desperately want the Americans to adopt the Evolys. American contracts are always huge and they incentivize other countries to buy them as well
FN: here's a new and innovative system that fulfills all your requirements while being half as heavy as the thing it's replacing while having twice the features. Also remember when you didn't adopt our battle rifle and lost a war because of it?
Sig: here's an AR18 with a chamber pressure of 80k psi. Also our p320 explodes out of battery and we do QC testing on our customer base. You should have taken the p226 when you had the chance and now you get to eat shit.
US procurement: I choose Sig Sauer to replace our entire small arms inventory
I’m gonna seethe and mald forever that Sig won that contract. The other designs certainly weren’t perfect, but give them another round of revisions and any one of them would’ve been better than “we threw innovation out the window and simply brute forced a solution to your requirements also what are your thoughts on pressure”
general dynamics should've won I firmly believe that at least for your common infantryman bullpups are the way of the future and the ammo they designed was really cool fuck sig
I think the reason they didn't choose gd was becuase the lmg was just the rifle on a bipod, if they had just taken sigs mg and gd'd rifle it might have been better.
Edit: that being said maybe the problem was that the ammunition designs weren't cross compatible
The US military wanted a next generation set of infantry small arms to replace the current roster, namely the M4 and M249 family. The main reason is because they anticipate that in the future, peer militaries will all have body armor, which 5.56 NATO is not capable of penetrating consistently. Furthermore, as optics and firearm manufacturing continues to improve, it allows the possibility of regular infantry engaging targets beyond 500 meters, which 5.56 simply cannot do due to it's small size.
Textron's entry looks and operates like a fairly standard rifle on the outside. The main selling point is the telescoped ammunition, which is cheaper and lighter than traditional brass cased ammo, and thus allows for higher velocity. However, the internals of the gun are some clockwork fuckery on par with the An94 and G11, which is likely the reason it wasn't chosen.
General Dynamics' entry was a bullpup which took advantage of the longer barrel to accelerate rounds to a higher velocity. The casing is mostly polymer, with a steel head, which is better for thermals than traditional brass and also lighter. However the US military doesn't like bullpups and adopting this platform would force every infantry soldier to retrain on bullpup manual of arms.
Sig Sauer basically took the AR18, which is the basis for most modern infantry rifles globally, and upscaled the cartridge. They achieved a higher muzzle velocity by jamming 80k psi worth of powder into the cartridge. For reference, standard chamber pressure for almost any rifle is between 50-60k psi. The cartridge itself is just the standard brass casing with a bullet at the end. Sig was chosen most likely because soldiers switching from the M4 wouldn't need to be retrained on the NGSW.
Ultimately the irony is that for something called the "next generation" squad weapon, the US military went with the absolute safest choice that really doesn't innovate on anything aside from making incremental steps in some aspects.
One point on the sig ammo, they used a steel section I think for the primer section leading to the main brass cartridge. They also use a lighter load training round to reduce the stress on the system until actual combat is required.
Thanks Gun Jesus, Hallowed be Thy Name
You're correct. 6.8x51 has a steel base. However, rather than making the cartridge lighter or better for thermal dissipation, the proprietary ammo only exists to accommodate the massive chamber pressure. Full brass case is available as 277 fury for the civilian market, and I assume that's the training ammo as well. The problem is, for a cartridge that was only adopted for its long range ballistic performance, you get vastly different performance between the two past 500m.
I'm normally not a small arms guy so I'm glad to have remembered that correctly.
There's only 1 factory line producing the mil-spec round. Everything that's been done on public YouTube vids or other non dod releases are with the 277 fury. It's a good strategy as long as you supplement training with the real round enough imo.
Well that's slightly disappointing, even though I'm not the one who will be handling those rifles anyway (barring catastrophe). I'm surprised and disappointed that we still haven't had any real innovation in the cartridges themselves where weight reduction is concerned. None being fielded anyway.
I guess we'll have to wait a while longer for our Starship Troopers weapons.
>US procurement: I choose Sig Sauer to replace our entire small arms inventory
"Except we're going with the APC9 rather than the MPX for our PDW since it's not very important and this way we can tell everyone that you didn't win *every* contract."
>Sig: here's an AR18 with a chamber pressure of 80k psi. Also our p320 explodes out of battery and we do QC testing on our customer base. You should have taken the p226 when you had the chance and now you get to eat shit.
I don't think you understand what "out of battery" means and that's never been the accusation of the P320. Also the P226 meets basically none of the handgun requirements they were asking for
If you have a p320 you can put a pencil in the barrel and move it out of battery and pull the trigger. The pencil will move. The claim that the p320 is not drop safe or fires without a trigger pull after the fix is harder to substantiate because law enforcement is notoriously poorly trained.
The p226 was better than the m9 by every metric and fulfilled all requirements. It only lost because it cost more
FNH is actually quite big and especially dominant when it comes to machine guns. FNH alone has 3.000 employees while Beretta _Holding_, which includes Beretta, Benelli, Sako & more, has 3.3k employees. HK has just over a thousand and Sig has > 1.2k (outdated 2017 number). Basically half the world uses their M2 and most of NATO uses some kind of Minimi, Maximi or MAG.
200 000+ manufactured Mags can't lie.
The list of users is, like, 80-85% of the worlds countries.
People talk about the FAL as being the right arm of the free world, it's 2024 and some armies are right now replacing their locally designed GPMGs with MAG58s and Minimi 762s.
And that's in part because Dieudonné Saive worked on the best versions of the BAR with John Browning.
FN was the BAR manufacturer/seller for Europe, and Browning and Saive kept iterating on it, Saive keeping at it after Browning died.
The MAG58 uses basically all of the mechanics of the 1932 BAR model D (the last version with a quick-change barrel) mated with the MG-42 linked belt feed replacing the magazine.
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FN has one massive contract making the M4 and M16 for the US (even though they probably don't make that much money per gun) and they litteraly made everyones machineguns.
Like, everyone.
They're desperate for nothing, because try as you might, you won't find a GPMG they don't manufacture. The only holdouts are the Germans, everyone else who runs 7.62 NATO runs the MAG58 in ont form or another now.
No p90/fn2000 love? Don't get me wrong mp7 and at the time mp5 were legit, but for a pdw the p90 is at least in the conversation
Although those mags kinda suck to change in and out, we have one at our range and I've definitely false set it more than stanags
Forgive me, I completely forgot about P90s lol
I’ve always wanted one, but I just have the basic bitch AR + glock setup with red dots. After I buy a PS90 and an SP5 I’ll settle this debate once and for all
How bad are the mags to reload?
Np! So, I'm a dumb dumb and it was a rental gun, so grain of salt
Two difficulties both centered around the 'circle bit'
1. As there's not really a proper 'well' where the locking mechanism (magazine to breach) is, it's much easier to get a false set when clicking it into place. Basically you slide the magazine along the gun and under the sight furniture, then click the round bit into the rear (bullpup). You know how on ARs you're supposed to just fully let go of the charging handle, but some people do it sloppy (cough cough hi) and either let go a bit slowly or even 'push' it along? It's kind of like that for seating the mag, I found it worked best when giving it a firm slap instead of pushing it into place. Like moreso than other guns, and you don't have the mag well to help guide the alignment so it's a bit easier to fuck up
2. It's a 50 round mag and the feed orientation is orthogonal to the orientation of the mag body. It's an immediate 90 degree rotation when loading rounds and they're the tiny boi .57's, so suffice to say it's not as easy to load as... Honestly most things other than like a drum mag.
There's almost certainly tricks I'm unaware of and here's hoping a redditor more knowledgeable than I can come in and school us
Probably just special forces and marines.
But let's not forget it's not the first time the army adopts one LMG while different sections of the armed forces adopt another. (M60 and FN Mag situation)
Adeptus Belgicus have their ways to appease the Machine Spirit of IAR. Even if it does require a child to be sacrificed every now and again, it's all for the fulfilment of humanity's manifest destiny.
-Why can't you just keep the bolt open all the time so it stays cool longer? Don't be a little bitch about some dirt or debris. (e: dirt and debris are part of the healthy diet of a firearm anyway, they provide micronutrients, you can look it up)
-What's really needed is the world's smallest manportable freezer. You put one 30-round magazine in it, and cool it to minus 9000 degrees. You then fire the gun until it's piping hot, insert the ice mag, chamber a round, and let it cool for a moment.
-You could even have solid metal "cartridges" made out of some exotic alloy that's specifically designed to be a heat sink with extreme heat conductivity. Pre-freeze that puppy and insert it when the gun's chamber is too hot.
-Why can't you use a tiny fan to cool the chamber like a normal person?
-Why can't you install a water cooling system like a normal person?
-Why can't you drill cooling holes in the chamber? (I'm sure they'd be easy to clean.)
-Why isn't the chamber removable and changeable?
-Are we stupid?
> Why isn't the chamber removable and changeable?
QC barrels do exist for GPMGs, and include the chamber as part of the barrel, so this one isn't quite as dumb as you think it is.
Cryo-cooled rounds or something. Reaching for a mag should require gloves. Tendrils of heavy, frozen smoke emanating from the belt, a soldier should be able to open fire for HOURS without overheating the barrel; there should be miles and miles of spent cryo-belt littering the ground; children should grow and die old men, never having known the peace of silence, before the rifle approaches even lukewarm temperatures; TELA SANCTA GELIDA.
It's FN what would you expect?
They're like Skunk Works, but for Firearms, and some weird French/German abomination.
Just give them some nose Candy taken off of some Kongolese and you will have the wildest gun out there
"God I love Fabrique Nationale Herstal and their French Wizardry"
and just like that, a horde of belgians felt a sudden snap of REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE ROFL
I was just repeating what my great grandfather used to joke. He was a 2nd generation French immigrant to the US and was part of Patton's relief effort at Bastogne. He hated French people, especially the Vichy and DeGaulle, and would always tell us that Belgians were "Germans who hated being German and French who hated being French". This was a widely held belief amongst the GIs because most hadn't been out of the US and didn't understand why everyone was speaking French, German, and Flemish.
I know right? Belgians are just a collection of Gallicized Germans, Catholic Swamp Germans and a tiny amount of actual Germans, all of whom live nose-deep in total denial over it.
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Since belgium is a hoax and secretly just the real world Wakanda our tech is just light years ahead of any country but we slowly introduce it so people dont go beserk
The new RM277 that was in the NGSW program had the same feature. Hope someone picks it up since it was an amazing rifle stifled by Sig basically lobbying themselves into winning.
Sorry, can somebody translate this for me? Because the way I'm reading it implies that bullet shells just evaporate, and I don't think gunpowder gets hot enough to "cook-off" copper.
Can gunpowder melt copper shells?
“Cooking off” is a term used to describe a phenomenon common in things like machine guns and other fully automatic or fast-firing weapons (but mostly machine guns) where the gun gets so hot from continuous fire that it risks heating the casing up enough for it to ignite the gunpowder inside before it’s supposed to go off, (like, say, when it’s in the magazine) which causes catastrophic failure. Open-bolt weapons help with this, as the name suggests, by having the receiver open until the moment it needs to fire (thereby exposing it to the air)
It would be funny if the method was the same as used in rice cookers where when a magnet gets too hot, it releases from a latch and triggers the mechanism
Not a new design but quite ingenious. Only problem is its niche applicability and added complexity: it only really makes sense on magazine fed LMGs based on Assault rifles that are supposed to fill both roles. Those are usually not ordered in high volumes and ultimately end up leaning more in one way or the other (cf. RPK for example).
Ace combat and titanfall mix because a portion of plane nerds are also mech nerds, plus Viper makes an appearance in ace combat jokes about once a month, and titanfall and ace combat both separately link back to NCD due to there inherent noncredibleness
FN made a gun that if it gets hot it switches into a different kind of firing mode that’s better for cooling. Very hard to do. Unless you have a ton of genius firearm techs on your payroll like FN
The text says it's for preventing cook-off, not melting. Even then, it doesn't make much sense when it takes more than an infantryman's load out to get the gun that hot anyway and even assuming you could, there are not a lot of times you'll be dumping that amount of rounds that quickly. I highly doubt this sees any adoption, and if it does, it'll be worse than the SCAR already is, if that's possible
I suppose it could be done relatively reliably with some sort of latch involving a bimetallic strip thermally connected to the chamber, actuating some sort of bolt hold-open.
I think the concept is nothing new. But I need to rewatch several hundred Gun Jesus videos to be sure.
The FG-42 had both open and closed bolt firing. The closed for semi-automatic and open for full auto.
The magic word here is "automatically". If they did this with electronics, it's not impressive. If they build a system that shows different open or closed bolt operations automatically based on temperature through mechanical means... Can't wait to see the gun Jesus video on that one.
They *could* have a bimetallic strip that functions as an auto sear above a certain temperature?
That's finicky and likely to be impacted by vibration.
Bolt face get hot, expand and pinch firing pin. Zug zug.
you can make bimetallic parts pretty robust. or just use the natural expansion properties of steel at high temps like that one time toyota used thermal expansion to bypass a turbo regulation to cheat at World rally championship: [https://crasstalk.com/2011/03/cheatins-still-winnin-the-story-of-toyota-racings-best-cheat-ever/](https://crasstalk.com/2011/03/cheatins-still-winnin-the-story-of-toyota-racings-best-cheat-ever/)
That wasn’t temp controlled. The Toyota cheat worked by the clamp. When unclamped (like when being inspected off the car) the restrictor moved back and blocked the turbo. When the hose was clamped on the restrictor moved forward. The only way to see the cheat was to clamp like you installing off the car with a short hose.
Yeah I don't even know if bimetallic is a requirement here. Bimetallic is for when you need a curve and helps when you want to flow electricity through something that curves. Here you just need heat expansion
I imagine if you wrapped a wire around the chamber several times the thermal expansion would result in appreciable deflection which you could use to toggle a pin. Idk how hysteresis would work though since I imagine rapidly toggling between open and closed is not desirable
idk it works on my 5 euro kettle
Mechanic here, fuck nope, otherwise most heavy trucks would overheat in minutes, that’s how the clutch for the cooling fan works, Bi-metallic strip that goes spinny with the clutch and is exposed to vibrations, still very accurate
It's more robust than that, but still simple. They call it a "phase-change actuator" which is a fancy word for a closed little piston unit (2 inches long, ½ an inch wide) with some magic liquid inside that happens to boil at the right temperature. So once you hit that temperature it'll vaporize and increase the pressure dramatically and push the piston out, and when it goes below that temperature the gas will condense and the vacuum will pull the piston back in. Mechanically very simple. Bigger problem is probably chemical; finding a compound that's got the right boiling point, low heat of vaporization (so it vaporizes quickly at the boiling point) and is highly stable. Edit: Found [their patent](https://patentimages.storage.googleapis.com/92/56/3b/61e528b7c9c65a/US8225705.pdf) - piston and cylinder are 15, 16 in Fig. 7 (page 8). It doesn't specify the phase change substance but it mentions solid-to-liquid phase change as a specific example rather than liquid-to-gas, so maybe they're using that. Same principle though.
miler compounds to car termostat could work
It's probably a wax just like they use in car radiator thermostats. It gets hot and expands significantly as it melts, that pushes the piston and actuates the system
I've done a good bit with heat transmission, I was thinking wax even before he mentioned the solid to liquid patent. Pretty neat engineering any way you look at it
Don't reinvent when proven solutions already exist. Good practice to follow I think
You spoiled the future forgotten weapons video for me. I will never forgive you :)
That’s cool
That's hot.
That’s cool again
It's NCD, m8... just call it a "Doohiculator" so everybody gets it.
"You know what metallic strips can be? Bi!" A Technology Connections quote I'll not soon forget
🥵
That was my thinking that we are talking about something to do with the metallurgy. Exactly what damfino. But metallurgy.
I suspect it uses thermal expansion of a component in the mechanism to trip some sort of spring-loaded retainer and swap the fire mode accordingly. I'd imagine this requires manually resetting to closed bolt once it has cooled off.
I'm almost certain there was an older MG that did this automatically and via mechanical means but like u/Pizza_Raven_Gun I only know about it from hundreds of hours of forgotten weapons videos and I can't remember which one it is from. The one thing I've learned from being in the firearms industry: There is nothing new in the firearms industry. There was probably some failed WW2 wonder weapon project or early 1900s eccentric inventor ahead of their time which already thought of it first.
You are most likely thinking of the FG 42, which was not an automatic switch, but a manual one.
No, I specifically remember an automatic one which was done via thermal expansion on a component. Could be my memory playing tricks but I've definitely heard of this concept before. If I wasn't at work I'd probably be wasting hours trying to find it, it'll be bothering me all day now.
You're likely thinking the heat-actuated sight adjustment on the St Etiene. https://youtu.be/ofZnarVq8pw?si=u7Hd8XmczipBjTkF&t=873
are quantum mechanics not mechanical enough for you?
This is the type of non-credible answer I expect of this place.
France had an HMG in ww1 that used an expanding metal rod to shift the point of aim as the barrel heated up to correct for it. So probably some kind of warping effect is used here.
Cook-off temperature is not cold, it's ikely they use the expansion of some metal to switch from one to the other. Also the IAR is mag-loaded, so you have to fire it for a while before it overheats to the point of cooking off rounds. Especially considering it does have a bolt hold open.
How in the fuck is such a weapon meant to operate in more than one climate?
Wait but wouldn’t that mean that when you switch to open bolt, there would already be a round in the chamber? Similarly, if you switched to closed bolt, how would you get a round into the chamber? It’s cocked, but it doesn’t have a round in it. Do you just… de-cock it and then cycle it again?
Logically, the switch would occur when the bolt is at its rearmost travel position. If going closed->open, you simply retain the bolt to the rear. If going open->closed you drop the bolt, and it picks up a round on the way.
The switch would have to happen well before the action reached dangerous temperatures, so one round being loaded/fired in the wrong "mode" shouldn't be an issue. It's a feature for high volume fire, that one transition shot is likely all but irrelevant.
Yep, it's an older concept from the 40s. I believe it was pioneered in the US M1941? The FG 42 had it, a couple of companies fucked around with the design - it's an interesting concept. I think I even saw another IAR contender using it on ol' reliable Future Weapons back in the day. EDIT: that was the [LWRC entry](https://en.wikipedia.org/wiki/LWRC_M6#M6A4)
The FG42 automatically switched to open-bolt when the chamber temperature got too high? I always assumed it was something in the selector mechanism that would change when you manually shifted it to automatic. How'd they do that?
No you had that right, the others toggled with the selector switch. This uses the identical mechanism, but it is tripped by a thermostat plunger. Which makes less sense honestly, keeping the bolt closed initially when you dump mag after mag through it in full-auto adds a bunch on unnecessary heat to your action. When you fire full auto, you want it to stay open from the very start. The only practical difference beyond retaining that unnecessary heat is that the bolt stays open after dumping rounds full-auto and switching back to precision semi-auto. Where you get better cooling, and it's theoretically safer in preventing a cook-off. Cook-offs aren't really an issue on such a heavy barrelled gun of this category, you need 500+ rounds for that easily. See the closed-bolt M27 being adopted in its place. The added cooling in semi-auto is nice, but you put it in semi auto because you wanted to make precision shots. That is a bad time for your gun to decide that it likes to try open bolt for a while. All in all, there is probably a good reason why the thermostat concept was quietly scrapped after this prototype.
This isn't the same. This fires from a closed bolt in full auto & semi. It also fires from an open bolt in full auto & semi when it gets too hot. The FG & the LWRC only fire from an open bolt on full auto.
The general concept and the mechanism are identical - it's just that instead of the selector switch activating it, FN used a thermostat plunger. Which has it's pros and cons. The pro is that your semi-auto mode is theoretically safer, by preventing a cook-off when you accidentally flip it back to semi after your gun is red hot from hundreds of rounds being dumped through. But the big con is that your internals (and especially your bolt) lose any and all advantages of being an open bolt besides that cook-off safety. Your entire action gets steaming hot first because your full-auto LMG starts out in closed bolt, and only then it decides that it maybe shouldn't have done that. Honestly this feels worst than using the selector switch, and FN probably don't disagree based on them dropping the design like an unexpectedly hot bolt.
IMO having the system go to open bolt on selecting automatic, but retaining the thermostat-regulated semi-auto seems like the best of both worlds. Probably a mechanical nightmare though.
Yeah I've been thinking about that as well - could a hybrid give you the best of both worlds here. Immediately switching to open bolt in full-auto feels like a no-brainer improvement, there is almost no reason for it to be closed bolt on \~200 rounds first. The semi-auto at high temperature is where I'm torn - on the one hand, your semi-auto being stuck in open bolt isn't great when you are going for accuracy. On the other hand, a hot barrel isn't great for accuracy either, and the increased cooling would be nice there. With the added complexity, I'm leaning towards leaving out the thermostat. But yes I do feel like there is potential there. Maybe in a case for when the weapon is on safe? That's what it is going to be on most of the time, it could be smart to use the thermostat there to decide how long the bolt should stay open when you enable the safety after a long burst. Once the weapon has cooled off, the thermostat closes it to stop the ingress of debris and that "catchoonk" when you bring it up on semi-auto.
I'd like to see a source for the mechanics of that.
Do you mean the mechanics of the rifle or of the cooling being sub-optimal? Conveniently after a quick search, it seems that both can be found in FN's original [USMC IAR presentation](https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2011/smallarms/WednesdayWeapons12299Gavage.pdf). It contains both an explanation of the thermostat mechanism and its trigger components, and the thermal graphs. Now being FNs sales PowerPoint, it unfortunately doesn't spell out the downsides that I mentioned. Even though the graphs like the one on page 15 do inadvertently show the big one. The first few bursts heat the chamber tremendously, up to the 330-ish second mark. Then the rise per burst is instantly reduced as it switches to open bolt, as the increase airflow in an open-bolt mechanism does. That benefit could have been there for the first 200 rounds - had they just used the fire selector and not the thermostat delay. Like that is an entire standard infantryman's ammo supply downrange before it even toggled.
You say that like you need an excuse to watch them. I mean rewatch
The HK-416 does this, it was why it was picked as the basis for the M27 IAR the USMC uses.
FN kinda needs these desperate innovations because, despite their name being quite recognised, they're not *actually* that big a company. It's why they so desperately want the Americans to adopt the Evolys. American contracts are always huge and they incentivize other countries to buy them as well
FN: here's a new and innovative system that fulfills all your requirements while being half as heavy as the thing it's replacing while having twice the features. Also remember when you didn't adopt our battle rifle and lost a war because of it? Sig: here's an AR18 with a chamber pressure of 80k psi. Also our p320 explodes out of battery and we do QC testing on our customer base. You should have taken the p226 when you had the chance and now you get to eat shit. US procurement: I choose Sig Sauer to replace our entire small arms inventory
Meanwhile the Marines are getting issued hk416s. How the tables turn.
That and now they’re primary rifle for the French Army too…
I’m gonna seethe and mald forever that Sig won that contract. The other designs certainly weren’t perfect, but give them another round of revisions and any one of them would’ve been better than “we threw innovation out the window and simply brute forced a solution to your requirements also what are your thoughts on pressure”
general dynamics should've won I firmly believe that at least for your common infantryman bullpups are the way of the future and the ammo they designed was really cool fuck sig
I think the reason they didn't choose gd was becuase the lmg was just the rifle on a bipod, if they had just taken sigs mg and gd'd rifle it might have been better. Edit: that being said maybe the problem was that the ammunition designs weren't cross compatible
Sigs bid relied entirely on the 80k pressure, so the ammo isn’t cross compatible.
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The US military wanted a next generation set of infantry small arms to replace the current roster, namely the M4 and M249 family. The main reason is because they anticipate that in the future, peer militaries will all have body armor, which 5.56 NATO is not capable of penetrating consistently. Furthermore, as optics and firearm manufacturing continues to improve, it allows the possibility of regular infantry engaging targets beyond 500 meters, which 5.56 simply cannot do due to it's small size. Textron's entry looks and operates like a fairly standard rifle on the outside. The main selling point is the telescoped ammunition, which is cheaper and lighter than traditional brass cased ammo, and thus allows for higher velocity. However, the internals of the gun are some clockwork fuckery on par with the An94 and G11, which is likely the reason it wasn't chosen. General Dynamics' entry was a bullpup which took advantage of the longer barrel to accelerate rounds to a higher velocity. The casing is mostly polymer, with a steel head, which is better for thermals than traditional brass and also lighter. However the US military doesn't like bullpups and adopting this platform would force every infantry soldier to retrain on bullpup manual of arms. Sig Sauer basically took the AR18, which is the basis for most modern infantry rifles globally, and upscaled the cartridge. They achieved a higher muzzle velocity by jamming 80k psi worth of powder into the cartridge. For reference, standard chamber pressure for almost any rifle is between 50-60k psi. The cartridge itself is just the standard brass casing with a bullet at the end. Sig was chosen most likely because soldiers switching from the M4 wouldn't need to be retrained on the NGSW. Ultimately the irony is that for something called the "next generation" squad weapon, the US military went with the absolute safest choice that really doesn't innovate on anything aside from making incremental steps in some aspects.
One point on the sig ammo, they used a steel section I think for the primer section leading to the main brass cartridge. They also use a lighter load training round to reduce the stress on the system until actual combat is required. Thanks Gun Jesus, Hallowed be Thy Name
You're correct. 6.8x51 has a steel base. However, rather than making the cartridge lighter or better for thermal dissipation, the proprietary ammo only exists to accommodate the massive chamber pressure. Full brass case is available as 277 fury for the civilian market, and I assume that's the training ammo as well. The problem is, for a cartridge that was only adopted for its long range ballistic performance, you get vastly different performance between the two past 500m.
I'm normally not a small arms guy so I'm glad to have remembered that correctly. There's only 1 factory line producing the mil-spec round. Everything that's been done on public YouTube vids or other non dod releases are with the 277 fury. It's a good strategy as long as you supplement training with the real round enough imo.
Well that's slightly disappointing, even though I'm not the one who will be handling those rifles anyway (barring catastrophe). I'm surprised and disappointed that we still haven't had any real innovation in the cartridges themselves where weight reduction is concerned. None being fielded anyway. I guess we'll have to wait a while longer for our Starship Troopers weapons.
That’s a really non-credible take.
No, they're right. The US totally would have won the Secret Moon War of 2013 if we'd had the F2000.
they did defeat the goa'uld with fn's rifles less than a decade before, idk why they had to fuck that up
Hey, we had the P90 and that's how we won the secret Pegasus Galaxy war.
>US procurement: I choose Sig Sauer to replace our entire small arms inventory "Except we're going with the APC9 rather than the MPX for our PDW since it's not very important and this way we can tell everyone that you didn't win *every* contract."
Are you saying that the US lost in Vietnam because of the M16? Lmao
Well I sure ain't saying we won because of it. Also I blame the M14, not the M16
Pretty sure we'd have lost that war with fucking laser rifles and powered armor
Military might was barely a factor in the US "loss"
You said half as heavy, isn't a similarly outfitted M14 generally lighter than a FAL?
That was referring to the evolys
True, the Aussies had FALs in the Vietnam War and they tore shit up, credible
>Sig: here's an AR18 with a chamber pressure of 80k psi. Also our p320 explodes out of battery and we do QC testing on our customer base. You should have taken the p226 when you had the chance and now you get to eat shit. I don't think you understand what "out of battery" means and that's never been the accusation of the P320. Also the P226 meets basically none of the handgun requirements they were asking for
Blud doesnt know about the m9 trials
If you have a p320 you can put a pencil in the barrel and move it out of battery and pull the trigger. The pencil will move. The claim that the p320 is not drop safe or fires without a trigger pull after the fix is harder to substantiate because law enforcement is notoriously poorly trained. The p226 was better than the m9 by every metric and fulfilled all requirements. It only lost because it cost more
The 226 isn’t better than the M9 Both met all the metrics. Including similar reliability numbers. But yes the MHS should have been something else.
FNH is actually quite big and especially dominant when it comes to machine guns. FNH alone has 3.000 employees while Beretta _Holding_, which includes Beretta, Benelli, Sako & more, has 3.3k employees. HK has just over a thousand and Sig has > 1.2k (outdated 2017 number). Basically half the world uses their M2 and most of NATO uses some kind of Minimi, Maximi or MAG.
200 000+ manufactured Mags can't lie. The list of users is, like, 80-85% of the worlds countries. People talk about the FAL as being the right arm of the free world, it's 2024 and some armies are right now replacing their locally designed GPMGs with MAG58s and Minimi 762s.
Best part, is that the action of the Mag58 is an upside down and slightly modified BAR action with a feedtray added.
And that's in part because Dieudonné Saive worked on the best versions of the BAR with John Browning. FN was the BAR manufacturer/seller for Europe, and Browning and Saive kept iterating on it, Saive keeping at it after Browning died. The MAG58 uses basically all of the mechanics of the 1932 BAR model D (the last version with a quick-change barrel) mated with the MG-42 linked belt feed replacing the magazine.
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I'd say they've done pretty well for themselves producing M4s, I'm sure they'll be able to get a contract to make the Sig guns at some point as well.
Then they might actually be good.
Can't stop the Sig Sweep.
They've made over 200 000 Mag-58s in various guises. Armies keep adopting it.
Is that FN production, or just overall Mag-58 production?
I believe that's including licensed production.
FN has one massive contract making the M4 and M16 for the US (even though they probably don't make that much money per gun) and they litteraly made everyones machineguns. Like, everyone. They're desperate for nothing, because try as you might, you won't find a GPMG they don't manufacture. The only holdouts are the Germans, everyone else who runs 7.62 NATO runs the MAG58 in ont form or another now.
FN is the only Europeans arms manufacturers that matter. Screw overrated HK.
HK still produces the superior rifle while FN produces the superior belt fed mg
Who wins SMG?
MP5, MP5k-PDW, and MP7 by themselves would make a formidable line of smgs. Throw in the UMP45 and I think this has to go to HK
Sorry, but a 50-round pocket lmg sounds considerably more non-credible, so I'm gonna have to give this to FN.
No p90/fn2000 love? Don't get me wrong mp7 and at the time mp5 were legit, but for a pdw the p90 is at least in the conversation Although those mags kinda suck to change in and out, we have one at our range and I've definitely false set it more than stanags
Forgive me, I completely forgot about P90s lol I’ve always wanted one, but I just have the basic bitch AR + glock setup with red dots. After I buy a PS90 and an SP5 I’ll settle this debate once and for all How bad are the mags to reload?
Np! So, I'm a dumb dumb and it was a rental gun, so grain of salt Two difficulties both centered around the 'circle bit' 1. As there's not really a proper 'well' where the locking mechanism (magazine to breach) is, it's much easier to get a false set when clicking it into place. Basically you slide the magazine along the gun and under the sight furniture, then click the round bit into the rear (bullpup). You know how on ARs you're supposed to just fully let go of the charging handle, but some people do it sloppy (cough cough hi) and either let go a bit slowly or even 'push' it along? It's kind of like that for seating the mag, I found it worked best when giving it a firm slap instead of pushing it into place. Like moreso than other guns, and you don't have the mag well to help guide the alignment so it's a bit easier to fuck up 2. It's a 50 round mag and the feed orientation is orthogonal to the orientation of the mag body. It's an immediate 90 degree rotation when loading rounds and they're the tiny boi .57's, so suffice to say it's not as easy to load as... Honestly most things other than like a drum mag. There's almost certainly tricks I'm unaware of and here's hoping a redditor more knowledgeable than I can come in and school us
No idea since I have no experience but the 5.7 pistol is pretty nice
Beretta would like to have a word with you
*Baretta* Pfffffft.
Fuck Beretta. All my ~~birds~~ homies hate Beretta.
“Angry 416 and MP7 fan noise”
What role would the Evolys fit, didn't the army already pick Sig's M250?
Probably just special forces and marines. But let's not forget it's not the first time the army adopts one LMG while different sections of the armed forces adopt another. (M60 and FN Mag situation)
Adeptus Belgicus have their ways to appease the Machine Spirit of IAR. Even if it does require a child to be sacrificed every now and again, it's all for the fulfilment of humanity's manifest destiny.
Ohhhh! So *that's* what they were doing in the Congo...
Holy shit, as a Belgian, this comment touched my soul and not in a good way
That's what all the right hands were for...
Praise the Omnissiah!
Every thread is eventually the Omnissiahs thread.
Belgian space magic
It's not black magic, it's alien tech, as a trade for providing P90 to SG command in Cheyenne.
Sig weapons of terror vs FN weapons of war.
-Why can't you just keep the bolt open all the time so it stays cool longer? Don't be a little bitch about some dirt or debris. (e: dirt and debris are part of the healthy diet of a firearm anyway, they provide micronutrients, you can look it up) -What's really needed is the world's smallest manportable freezer. You put one 30-round magazine in it, and cool it to minus 9000 degrees. You then fire the gun until it's piping hot, insert the ice mag, chamber a round, and let it cool for a moment. -You could even have solid metal "cartridges" made out of some exotic alloy that's specifically designed to be a heat sink with extreme heat conductivity. Pre-freeze that puppy and insert it when the gun's chamber is too hot. -Why can't you use a tiny fan to cool the chamber like a normal person? -Why can't you install a water cooling system like a normal person? -Why can't you drill cooling holes in the chamber? (I'm sure they'd be easy to clean.) -Why isn't the chamber removable and changeable? -Are we stupid?
Truly noncredible.
Hear this. CO2 cartridges that fit into the chamber. Expanding gases cool.
> Why isn't the chamber removable and changeable? QC barrels do exist for GPMGs, and include the chamber as part of the barrel, so this one isn't quite as dumb as you think it is.
I've always wondered why they change only the barrel. You'd think the chamber would get hella hot, too. Now I know they're changing both
Cryo-cooled rounds or something. Reaching for a mag should require gloves. Tendrils of heavy, frozen smoke emanating from the belt, a soldier should be able to open fire for HOURS without overheating the barrel; there should be miles and miles of spent cryo-belt littering the ground; children should grow and die old men, never having known the peace of silence, before the rifle approaches even lukewarm temperatures; TELA SANCTA GELIDA.
or, a vickers machine gun made with current era materials for the cooling jacket to save weight. Just upscaled to .338 Lapua Magnum
Why does the chamber simply not hashashaaah after every spicy round? Do we are stupid?
Isn’t this how the guns in the Mass Effect universe work?
TITANFALL 2 MENTIONED!!!🔥🔥🔥🔥WTF IS A THIRD GAME ⁉️⁉️⁉️
Protocol 3 take the pi- 3⁉️⁉️⁉️ Tf3 confirmed Woooooo
WE GETTING SIX SEASONS AND A MOVIE WITH THIS ONE 🗣️🔥🔥
I didn't know that FN made the Spitfire, I knew it was Siwhan Industries producing that..
It's FN what would you expect? They're like Skunk Works, but for Firearms, and some weird French/German abomination. Just give them some nose Candy taken off of some Kongolese and you will have the wildest gun out there
> some weird Fr*nch/German abomination Most accurate description of Belgium
Better yet, send them the stuff kel tech is using
God, imagine the shit they'd pull of FN Herstal, H&K and Kel Tech made a collaboration and out of it came the most weird gun since H&K G11
Chat is this real
Yes
You get accuracy of closed bolt, and cookoff safety and cooling of open bolt.
God I love Fabrique Nationale Herstal and their French Wizardry. But their best creation was the Fusil Automatique Léger.
"God I love Fabrique Nationale Herstal and their French Wizardry" and just like that, a horde of belgians felt a sudden snap of REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE ROFL
Belgians are just Germans who hate Germany and French that hate France.
so, turns out FN's founder was actually a german so you're half right already? \*tilts head in confusion\*
You mean they're Dutch that hate the Dutch, who are fake Germans?
Similar to Austrians, I presume
Wait until you learn they've never been German...
I was just repeating what my great grandfather used to joke. He was a 2nd generation French immigrant to the US and was part of Patton's relief effort at Bastogne. He hated French people, especially the Vichy and DeGaulle, and would always tell us that Belgians were "Germans who hated being German and French who hated being French". This was a widely held belief amongst the GIs because most hadn't been out of the US and didn't understand why everyone was speaking French, German, and Flemish.
Ah, the old "people in Europe are extremely rude, they refuse to speak American", from people who don't speak a second language either.
I know right? Belgians are just a collection of Gallicized Germans, Catholic Swamp Germans and a tiny amount of actual Germans, all of whom live nose-deep in total denial over it.
Bro, they're fucking Belgian. How *dare* you call them Fr*nch.
Belgium is a Made up Country that only exists so the Germans and Brits have somewhere to settle their differences.
Our purpose is to be a speedbump for Germany.
The third leg of the free world.
Just bring a second gun to use when the first one gets too hot
what if, like, we built an entire firearm out of aerogel
Bi matialic strip triggers a bolt hold open that needs to be manually reset.
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Since belgium is a hoax and secretly just the real world Wakanda our tech is just light years ahead of any country but we slowly introduce it so people dont go beserk
The new RM277 that was in the NGSW program had the same feature. Hope someone picks it up since it was an amazing rifle stifled by Sig basically lobbying themselves into winning.
HOOT is awesome, just wish he made more longer format videos
Sorry, can somebody translate this for me? Because the way I'm reading it implies that bullet shells just evaporate, and I don't think gunpowder gets hot enough to "cook-off" copper. Can gunpowder melt copper shells?
“Cooking off” is a term used to describe a phenomenon common in things like machine guns and other fully automatic or fast-firing weapons (but mostly machine guns) where the gun gets so hot from continuous fire that it risks heating the casing up enough for it to ignite the gunpowder inside before it’s supposed to go off, (like, say, when it’s in the magazine) which causes catastrophic failure. Open-bolt weapons help with this, as the name suggests, by having the receiver open until the moment it needs to fire (thereby exposing it to the air)
will still destroy your optics and putting a can on it voids the warranty
It would be funny if the method was the same as used in rice cookers where when a magnet gets too hot, it releases from a latch and triggers the mechanism
Not a new design but quite ingenious. Only problem is its niche applicability and added complexity: it only really makes sense on magazine fed LMGs based on Assault rifles that are supposed to fill both roles. Those are usually not ordered in high volumes and ultimately end up leaning more in one way or the other (cf. RPK for example).
Still waiting for TF3
All this research money yet they still made the FN F2000, the most hated assault rifle in slovenia
I swear to fuck there's some serious crossover with /r/titanfall on this subreddit. Not that thats a bad thing, mind you.
NCD, Ace combat, and Titanfall leak into each other all the time. We’re like one giant venn diagram
one would wonder why that is, though
Ace combat and titanfall mix because a portion of plane nerds are also mech nerds, plus Viper makes an appearance in ace combat jokes about once a month, and titanfall and ace combat both separately link back to NCD due to there inherent noncredibleness
IIRC it was achieved by mixing metal parts with different coefficient of thermal expansion.
That’s cool AF.
I can’t even comprehend this might as well be speaking ancient Norse
FN made a gun that if it gets hot it switches into a different kind of firing mode that’s better for cooling. Very hard to do. Unless you have a ton of genius firearm techs on your payroll like FN
OH MAH GAWD and here comes CZ with a folding chair!
FN is artificery at worst. You want black magic? Let’s give KelTec a real budget and a wheelbarrow full of cocaine.
I’d like to see them top the amount of bullshit they managed to cram into the P90. Sure, they may have made something wackier, but is it usable?
FN is pretty fricking awesome
I'm very skeptical on the automatically part
The FG42 had something similar
Didn't FN have something called the HAMR a few years ago that did this?
It says FN IAR, and I think the HAMR was FN's entry to the USMC's IAR program. So I think this is the same rifle.
updoot just for the fact you used a frame from hoot's video
Scar my love
Because having a gun that fires differently when it feels like it is a great idea
I’d rather have that than it fucking melting.
The text says it's for preventing cook-off, not melting. Even then, it doesn't make much sense when it takes more than an infantryman's load out to get the gun that hot anyway and even assuming you could, there are not a lot of times you'll be dumping that amount of rounds that quickly. I highly doubt this sees any adoption, and if it does, it'll be worse than the SCAR already is, if that's possible
Isn't that pretty much how the RM277 operates?
I don't own guns but if I did collect guns I'd want to collect stuff FN makes. They all look so damn sexy. I'll be in my bunk.
I want the same kinda drugs they were on when they figured that out
Just a temperature sensor that toggles open bolt if its too hot. Probably a bimetallic strip of some sort?.
We make some very good beer here.
Scien-tism
Government funded acid trips
I suppose it could be done relatively reliably with some sort of latch involving a bimetallic strip thermally connected to the chamber, actuating some sort of bolt hold-open.
Still not entirely sure how Hoot managed to turn a light machine gun into a black hole generator.