Machine gun mechanics question

[Malidictus]

When I say "mechanics", I'm referring to the realism aspect of how the firearms are supposed to operate within the fiction of the game. This is likely to be pedantic and I'm not really that well-versed on the subject. But hey - that's why I'm asking :)



I've been playing around with the HMG recently, and noticed an odd thing. It seems to be a closed-bold system. It made me wonder why that is. I went back to the other two MGs (Stalwart and MG-43) to check what they are. The Stalwart is definitely closed-bolt, though for that it makes sense. It's essentially an oversized, belt-fed rifle in the style of the RPK. The MG... I'll get to in a bit, since it's weird.

It made me wonder why the HMG is closed-bolt. Arrowhead brag about the realism of their fictional firearms, so why would a high-calibre (looks to be .50 cal equivalent) machinegun fire from a closed bolt? The reason LMGs generally fire from an open bolt is for the sake of cooling - the bolt is open to the air and so has a chance to cool passively, where a closed bolt traps heat to an extent. That's important for a high volume of fire weapon like a machinegun. Meanwhile, the benefits of a closed bolt are less important - lighter trigger pull, faster trigger response and keeping dirt out of the inner workings. Wouldn't it make more sense for the HMG to fire from an open bolt?



An then there's the MG-43. I genuinely don't know what configuration that uses. I thought it was an open bolt and it certainly looks like it from the side. However, my character never operates the weapon's charging handle - even when reloading from empty. I don't know enough about firearms to tell just from looking at a fictional gun. Mostly, I rely on the direction of the charging handle rack to determine bolt position. Both the Stlwart and the HMG are racked back first then forward, meaning open bolt then close bolt. I was expecting the MG to work backwards, but I can't tell.

If anyone has additional information on the subject, please let me know. This is supremely unimportant, but it's interesting to me :)

[StormhawkV]

The devs apply their idea of 'realism' in a very selective way. Basically if it would help the player they ignore it but they can't give the HMG more ammo because the drum is too small to hold more. It's not only an entirely made up problem it's also asinine to waste time on this while your game has this many issues. I also doubt any of the devs responsible for designing the weapon models knows the difference between open and closed bolt systems.

[vanillahapynis]

This is also a game that lets us one-hand a full-auto high calibre SMG with a side mounted magazine, but not our bullpups.

AP ammo somehow does less damage.
The charging handle for the breaker(s) is in-line with the barrel.
Plasma weapons don't melt or otherwise burn enemies, same with laser weapons.

I gave up on this idea of "realism" a little while ago.

If i had to say what the MG43 uses though, i would look at the real world parallel i see it as, the MG42 which was roller locked iirc.

[nizzemancer]

Originally posted by Malidictus:

When I say "mechanics", I'm referring to the realism aspect of how the firearms are supposed to operate within the fiction of the game. This is likely to be pedantic and I'm not really that well-versed on the subject. But hey - that's why I'm asking :)



I've been playing around with the HMG recently, and noticed an odd thing. It seems to be a closed-bold system. It made me wonder why that is. I went back to the other two MGs (Stalwart and MG-43) to check what they are. The Stalwart is definitely closed-bolt, though for that it makes sense. It's essentially an oversized, belt-fed rifle in the style of the RPK. The MG... I'll get to in a bit, since it's weird.

It made me wonder why the HMG is closed-bolt. Arrowhead brag about the realism of their fictional firearms, so why would a high-calibre (looks to be .50 cal equivalent) machinegun fire from a closed bolt? The reason LMGs generally fire from an open bolt is for the sake of cooling - the bolt is open to the air and so has a chance to cool passively, where a closed bolt traps heat to an extent. That's important for a high volume of fire weapon like a machinegun. Meanwhile, the benefits of a closed bolt are less important - lighter trigger pull, faster trigger response and keeping dirt out of the inner workings. Wouldn't it make more sense for the HMG to fire from an open bolt?



An then there's the MG-43. I genuinely don't know what configuration that uses. I thought it was an open bolt and it certainly looks like it from the side. However, my character never operates the weapon's charging handle - even when reloading from empty. I don't know enough about firearms to tell just from looking at a fictional gun. Mostly, I rely on the direction of the charging handle rack to determine bolt position. Both the Stlwart and the HMG are racked back first then forward, meaning open bolt then close bolt. I was expecting the MG to work backwards, but I can't tell.

If anyone has additional information on the subject, please let me know. This is supremely unimportant, but it's interesting to me :)

In real life firing a closed bolt system reduces first-shot inaccuracy and lock-time as well as having cleaner operation.

Closed Bolt MG examples:
M2 Browning
Vickers MG
Maxim MG
Lots of German WW2 aircraft-MGs

Open Bolt MG examples:
PKM
MG34
MG42
M60
FN MAG/M240
FN Minime/M249
Stoner 63
BAR

This is a future sci-fi civilization that could have any number of materials and technologies that are unavailable to us, that's your reasoning.

[Postman Pat]

The problem, of course, with "This is a future sci-fi civilization that could have any number of materials and technologies that are unavailable to us, that's your reasoning" is: if this is the case, why do we not have some sort of hyper-munition that can pierce any surface? If we're going to enter the realm of "magic materials" then, well, let's do it, right?

Of course there could be other in-universe explanations like "since both of the 'wars' are basically an endless MIC money sink to keep humanity united [ala 1984], the equipment is purposefully subpar so the Helldivers can never *actually* win."

But then, why equip them with what must be extremely costly and armed and staffed battleships? I dunno.

[Malidictus]

Originally posted by nizzemancer:

In real life firing a closed bolt system reduces first-shot inaccuracy and lock-time as well as having cleaner operation.

Yeah, I mentioned as much. With an open bolt weapon, the bolt is held back while ♥♥♥♥♥♥. Pulling the trigger slams the entire bolt assembly forward to chamber the round, which puts a jolt into the weapon and takes some time between trigger pull and shot. Hence why most small arms use a closed bolt system.

Originally posted by nizzemancer:

This is a future sci-fi civilization that could have any number of materials and technologies that are unavailable to us, that's your reasoning.

Normally, sure. However, Arrowhead have taken pains to try and model realistic firearms, arguing about the number of rounds which can physically be housed within a magazine with the size shown in-game, or argued about why a man-portable Minigun wouldn't work due to recoil, etc. I'm trying to discuss ballistic firearms within the context that Arrowhead themselves have established.

Originally posted by vanillahapynis:

The charging handle for the breaker(s) is in-line with the barrel.

This is where my limited knowledge of firearms comes short, but why is that a problem? As far as I know, the charging handle is physically attached to the bolt carrier, which is itself in-line with the barrel. Can you give me a but more context there?

Originally posted by vanillahapynis:

If i had to say what the MG43 uses though, i would look at the real world parallel i see it as, the MG42 which was roller locked iirc.

The MG-43 (like the MG-94 from Helldivers) is based on the German MG-42, as far as I know, so this makes sense. I was more curious about the weapon's operation, though. The MG-42 still has a charging handle on the side for racking the bolt, although its operation is kind of weird. I would have expected the MG-43 in Helldivers to similarly have a working charging handle, but our characters never operate it.

What's weird is I seem to recall needing to rack the MG-43 in the past, but that didn't seem to be the case when I was testing it for this thread. I wonder if the animation changed when Arrowhead shortened it with the last patch? That would be odd, considering the HMG retained its bolt rack - the character just does it faster.

[TheAceOfSpodes]

So there's no real technical reason a machine gun MUST be open bolt. As someone pointed out earlier, there are a number of solid designs that fire from a closed bolt.

However, there are some practical reasons that seem to make it the more viable option. And I apologize for the gratuitous use of the words "generally" and "tend to" in the coming explanation, because there's always one or two examples that defy the trend.

For starters, simplicity. Putting a gun through that volume of sustained recoil (especially on larger caliber MGs) is very stressful on a gun. Open bolt systems have (generally) fewer moving parts. There's no hammer/striker, and they tend to use fixed firing pins. Less small moving parts, less things break.

Second, better heat management. In a closed bolt weapon, if you stop firing mid belt/magazine, you have a round inserted into the chamber, and the bolt is closed and locked. In a weapon like a machine gun, this introduces the very real possibility of something called a "cook off", when the heat from the chamber of the weapon is enough to cause a round to fire off. That's a pretty big safety issue, you'd need to sit there for an extended period if you cease firing mid belt/magazine ensuring your weapon was pointed in a safe direction. You see this problem occurring when clearing jams in open bolt weapons. Sometimes that round cooks off when its just barely left the chamber, and injuries tend to result.

Third, open bolt offers a theoretically higher rate of fire. Without having to activate a striker or hammer, you can skip a few microseconds of operation. In practical terms, this doesn't really come into play since rate of fire is mostly regulated by other systems/mechanisms, like bolt weight, bolt movement, gas systems, that sort of thing. But it is *technically* a faster method of operation.

[vanillahapynis]

Originally posted by Malidictus:

This is where my limited knowledge of firearms comes short, but why is that a problem? As far as I know, the charging handle is physically attached to the bolt carrier, which is itself in-line with the barrel. Can you give me a but more context there?

What i mean by it being "in-line with the barrel" is that when you look at the breaker(s), the charging handle is taking up space where a part of the barrel should be.

Something else that bugs me is that the MG43 and HMG feed from the right and eject to the left. Despite most other weapons being right handed.

And I have no idea why AH doesn't show our character interacting with the MG43s charging handle, probably an oversight.

Also it should be noticed, the MG43 has no gas tube, which further reinforces the idea it uses something based on recoil to operate. If that weird stock/bipod thing under the barrel is meant to be the gas tube though, then it would be a (very) long stroke gas piston. And a very poorly designed one at that since there appears to be no way to remove said gas tube.

[Malidictus]

Originally posted by vanillahapynis:

What i mean by it being "in-line with the barrel" is that when you look at the breaker(s), the charging handle is taking up space where a part of the barrel should be.

Ah, gotcha. Charging handle looks to be clipping with the barrel? I'll have a look next time I'm in-game.

Originally posted by vanillahapynis:

Something else that bugs me is that the MG43 and HMG feed from the right and eject to the left. Despite most other weapons being right handed.

You know... that didn't even register with me. They're right-handed weapons, yet they're ejecting shells into the shooter's left forearm. That one I think may be a stylistic choice. The standard camera position is over the Helldiver's right shoulder, so putting the more interesting weapon elements on the left makes sense. Granted, the game also has a first-person mode, but I don't think as many people use that.

Originally posted by vanillahapynis:

Also it should be noticed, the MG43 has no gas tube, which further reinforces the idea it uses something based on recoil to operate. If that weird stock/bipod thing under the barrel is meant to be the gas tube though, then it would be a (very) long stroke gas piston. And a very poorly designed one at that since there appears to be no way to remove said gas tube.

Didn't even think about that. I actually know very little about gas-operated firearms, as most of my knowledge is second-hand (World of Guns, movies, YouTube videos, etc.). If you have the time, could you go into a bit more detail on that?

[Koala 4peace]

Also not an expert, but since you made the comparison with a 50. cal, the legendary M2, at least in the HB variant, fires from a closed bolt.

[Malidictus]

Originally posted by Koala 4peace:

Also not an expert, but since you made the comparison with a 50. cal, the legendary M2, at least in the HB variant, fires from a closed bolt.

It does? I definitely need to go back World of Guns, then :) Thanks for the heads-up. I guess that explains why the HMG fires from a closed bolt. It's sci-fi, but it very much feels like Arrowhead based it on the Ma Deuce. Now I just have to figure out why my character closes the top cover mid-reload, only to immediately open it up again...

[vanillahapynis]

Originally posted by Malidictus:

Didn't even think about that. I actually know very little about gas-operated firearms, as most of my knowledge is second-hand (World of Guns, movies, YouTube videos, etc.). If you have the time, could you go into a bit more detail on that?

I'm not really sure what i could explain that isn't to be found elsewhere, especially since im not very good at describing concepts and such.

This video gives a bit of info on how long-stroke gas pistons work. The channel itself also has a playlist showing how various other mechanisms to do with firearms work.

https://youtu.be/ASM0IAfoQzQ?si=113eRMGXIQt-oK3D

[Footman]

Closed bolt suggests caseless ammunition has been refined even for high caliber/mm rounds.

[Malidictus]

Originally posted by vanillahapynis:

This video gives a bit of info on how long-stroke gas pistons work. The channel itself also has a playlist showing how various other mechanisms to do with firearms work.

Forgotten Weapons is a good choice, yes. Thank you for the link, that's a pretty good explanation. Seems like the system isn't as complicated as I thought - literally just a piston in a tube. Seeing the bolt carrier, piston and charging handle all in one chunk of machine metal was quite helpful.

From what Ian said, your initial guess seems reasonable - that the MG-43 is some kind of long stroke piston design. It generally feels like a very "low-tech" weapon in pretty much every way, so this makes sense.

[DoktorFar]

Originally posted by Malidictus:

Wouldn't it make more sense for the HMG to fire from an open bolt?

Normally yes, but in this case, no. The reason is the tiny magazine of the HMG. It has very few rounds and it doesn't have a high firerate. and it takes ages to reload. So for these reason I conclude that the HMG wold not overheat.

It's not a great weapon imo and much less use than the autocannon even though the patch changes does move it closer to that same role as the autocannon. Ironically the HGM ends up with almost LESS ammunition than the autocannon, which is hilariously weird. While also missing out on the autocannons very nice zoom magnification in 1st person view as well as its amazing long range OP heavy sniping capabilities.

[vanillahapynis]

Originally posted by Malidictus:

Forgotten Weapons is a good choice, yes. Thank you for the link, that's a pretty good explanation. Seems like the system isn't as complicated as I thought - literally just a piston in a tube. Seeing the bolt carrier, piston and charging handle all in one chunk of machine metal was quite helpful.

From what Ian said, your initial guess seems reasonable - that the MG-43 is some kind of long stroke piston design. It generally feels like a very "low-tech" weapon in pretty much every way, so this makes sense.

My guess was that it was roller locked, which i believe is correct after some quick testing just now.

You'll notice the MG43's charging handle is non-reciprocating, your character also only uses it if you use up all of the rounds in the magazine (much easier to see in first person).
So we can assume from this that the MG43 fires from a open bolt like the MG42, and uses a similar system to the roller lock, which is why it has no gas tube. That thing under the barrel is simply furniture.

Also of note, is that the MG43 has a quick-change barrel from the looks of it, which further supports the idea it uses recoil to operate. The only thing it's missing is a muzle-booster.