Has Anyone Ever Made a Belt-Feeding Machine Gun?

[PureSilver]

First, this isn't a project log at all (I've too much on my plate at present) but an idea I was wondering if anyone had ever tried. My guess is that there are film props that use this system, but I've never seen an airsoft gun using it. Maybe someone will take this idea and run with it (or maybe they'll donate a shagged G&P M249 to me) so at least it will get built.
 
Essentially, as we all know, many belt-fed machineguns have an exposed feed - that is, the belt is visible from the outside of the gun. When they're fired, the belt feeds through the operating mechanism and spits itself (as disintegrated links, or empty belt, and expended cartridge casings) from the ejection port. The key thing here is that the belt moves as the gun is fired, feeding out of the magazine and into the action of the gun. Obviously, in airsoft guns, this isn't the case at all; no airsoft weapon I've ever seen has been truly belt-fed (and, as below, I don't think it's probable that one ever will) and airsoft replicas often have a token stretch of belt which doesn't move at all. Compare the absolute awesomeness and the comparative lameness:
 

 

Spanish Navy FN Minimi

 

 

G&P M249 Para

 
There are a number of reasons for airsoft replicas not to belt-feed. The first is that there are very few airsoft guns which keep their BBs in a shell (which a true belt-fed gun would) because it's annoying picking up the expended shell casings. That problem is annoying with a bolt-action, but it would be orders of magnitude worse with a multi-hundred-RPM fully-automatic machinegun. Even if the belt-fed gun was based on a shell-ejection system, the visible part of the belt (feeding into the action) would appear to be of expended rounds, because airsoft shells don't have a bullet tip visible. Even if that problem could be solved (say, by a partial 'bullet') no airsoft gun has the power to delink (disintegrating link) or separate (non-disintegrating link) belted ammunition. Even if that problem could be solved, the cartridges (with their faux bullet intact) would not fit through the ejection port. So there's very good reasons for never having made a belt-fed airsoft gun.
 
However.

Most machineguns are now designed to be man-portable as well as pintle-mounted, which means that they must carry their ammunition in boxes and sacks attached to the gun itself. Because belted ammunition dislikes being bent in the horizontal plane, most designs mount the ammunition carrier inline with the belt feed, often directly beneath the feed tray. So, what is to stop someone from designing an airsoft gun that feeds its ammunition belt out of its magazine, into the feed tray, and then straight down and back into the magazine? The two ends can be relinked to form a loop that can be rotated by stepper motors, moving one cartridge for every shot the weapon fires. Here's a very rough model using an M249 (base model credit to Master-0f-God) to explain what I mean:
 

 
Here's a slightly-zoomed in version to illustrate the loop of linked ammunition:
 

 
As you can see, the idea is that the belt creates a closed loop which can be rotated out of the magazine and into the action (so that the visible portion of the belt will move just like in the RS gun), and then, hidden from view, back down into the magazine. Thus an airsoft magazine can have enough belt to match one cartridge's rotation to each of the thousands of BBs in the magazine. This is a very crude model; in practice, some bearings and guides would be necessary to guide the belt through the relatively tight turns successfully, and of course a pair of motorized sprockets (not unlike the gears on a bicycle) will be needed to grip the cartridges and move the belt.
 
I chose the Minimi for a few reasons. First, it has a simply vast internal volume which means the BB gearbox can be sat much further back so it won't interfere with the belt-cycling mechanism. Hopefully an inner barrel will be simply threaded inside the loop; there's plenty of room inside for such an arrangement without the belt interfering with the inner barrel. Secondly, by my reckoning there's enough room in the cavernous M249 box magazine for such an arrangement plus a reduced BB load, and thirdly the method of attachment of the box magazine to the M249 is very tight, so that the return feed for the belt should be well hidden.
 
As to the rest of the arrangement, I'm foreseeing the BBs being fed upwards through the 'well' rather than through some horrible flexi-pipe arrangement outside the gun. It will be a bit of a pain in the *albartroth* to delink the loop and detach the magazine altogether, plus the magazine (with all these components inside it) would be pretty expensive. Better, I think, to just be able to pour BBs into the magazine to reload it.

 

What do we think? Waste of time? Or cool high-end feature?

[Yuri]

I believe some classic MG34, might've been Asahi, had a system that sort of rattled the belt to make it seem like it was being fed into the gun, but nothing like this. 

 

I like it. It's a cool idea that seems totally doable. Like you said, there's plenty of room for it.

[ollie_ty]

Id go slightly further down into the mag with the loop. That way, your entire high cap mechanism can sit within the loop.

[PureSilver]

Cheers - and ollie_ty, you could well be right. I've not much familiarity with the inside of box magazines (a position known as 'the moral high ground', I believe). The only question remaining is, is there enough space left in the magazine for an 8c.i. tank filled with propane and acetylene? Because if there is, with a spark plug, a solenoid, and a link to the fire-control unit that would manage the belt's rotation, the gun could also do this:
 
http://www.youtube.com/watch?v=siK5_WxiORY

 

(Just joking. I think. I don't know how much gas you need to run one of those things. If it was an M240 that was being converted, maybe.)

[aznriptide859]

^I want that for reasons unknown lol.

[ollie_ty]

I want that in ALL OF MY GUNS

[Kenworth W900]

Damn - you could make newbs *suitcase* some serious bricks with that :D

[PureSilver]

Yeah, I should think there'd be a few brown trousers...

 

 

Looks like you need both oxygen and fuel (butane, propane, acetylene, LPG - almost anything, apparently) plus a coil, a spark plug, and an FCU. Nothing too complicated, but quite demanding in terms of space. I reckon it would fit in a big ammunition box just fine, but it would be pretty heavy...

[QQexDERA]

Re-enactment groups have been doing this for donkey's years ('cos let's face it, Mr Plod and the Home Office aren't going to be massively happy about Sec 5 licensing 2cm Flak 30's for live fire by a bunch of WW2 kit wearing loons - and thats speaking as someone who used to be one of those loons!). The pain in the *albartroth* bit is getting the propane/oxy mix right, reliably. You wouldn't believe how much fettling it takes to get that sorted (having seen nunerous kits used over the years). WW2steel.com in the US do them, and WTAC do them over here (some small enough to be mounted in SMG's - though the tanks have to be stuffed elsewhere)

 

As to the original question, yes, someone has made an Airsoft belt-fed, but it was a full auto 40mm MOSCART GMG.

[PureSilver]

Chemically speaking, I suppose you need a simple 1:5 propane:oxygen mix for complete combustion, but I can imagine it being a complete nightmare to get that mix out reliably. I wonder how many shots you get from the tanks? And how many you would get from (say) a pair of 8c.i. tanks (probably not enough to make a viable handheld weapon).

 

I'd be interested to see that GMG, though!

[Azubi]

I remember, as a little kid, having a toy belt-fed that used the exact system you have shown in the original post. It was AWESOME. An airsoft version wold look good too I reckon, seems an awful lot of work for such a small detail but fair play for it!

[Murdoc]

I believe some classic MG34, might've been Asahi, had a system that sort of rattled the belt to make it seem like it was being fed into the gun...

Thought the same while reading the topic title...

Much better idea, than Asahi's... I wish you good luck...

Haha... quite funny...

[PureSilver]

Ha! That's pretty bad, but worth seeing. I reckon it would be a lot more convincing with just a short stretch from an underslung box magazine, but I guess those hadn't been invented by 1945.

 

Sadly, though, I don't have the time or the money. It's all in my head, but it ain't happening yet. Anyone with a ratty G&P M249 trust me enough to let me work on it for free?

[QQexDERA]

Not underslung, but both the MG34 and MG42 could feed from a 50 round drum that clipped onto the end of the feed plate. With one in place, the Shoei's wobbling ammo belt doesn't look quite as bad.

[Darkmikey22]

hmm i like it!, why didnt i think of this when building the gpmg!. getting the rounds to look like they are moving from a 50rd box tin could be an intreesting idea. but would need to know how they did it on the asahi's mg42.

ok its not great compared to your idea but it still looks better than the rounds just sitting there.

may have to seriously ponder on this idea.

now look what youve made me do PURESILVER! im nearly at the finishing stages of the gpmg, thn you throw this in the works lol

[viallet]

A few years ago we had a simfire module hooked up to a killbucket template M2HB.  Obviously a little inexperienced in the fire control we had some issues.  The principle one was the solenoid for the propane canister we used for combustible freezing open in the 90+% humidity and the ABS outerbarrel or perhaps the paint on it catching fire.  The propane did more muzzle flash than blast, lit unreliably but was still cool.  The barrel was a complete loss.  The body survived in a slightly warped fashion...  

 

Sadly I have yet to revamp the project, I've always thought that perhaps a propane powered gas blowback mechanism with a ignition mechanism at the end of a metal barrel might work - I just never seem to find the time.

[PureSilver]

That's very interesting... Can I ask how big the gas tank you needed was for the M2HB? Did you have external oxygen, or did you just run the gas past a venturi for outside air?

 

Maybe someone with a remote trigger set up and several brick walls to hide behind should try sticking a blowtorch at the end of a steel-internalled WOC. I'm pretty sure it would explode, but it would be pretty cool in slow motion if nothing else.

[blobface]

Maybe someone with a remote trigger set up and several brick walls to hide behind should try sticking a blowtorch at the end of a steel-internalled WOC. 

I've always wondered if someone could use the propane coming out of the gbb system to be recycled, ignited, and led back to the magazine / magwell area to warm up the magazine for people in countries with real winters.. sounds like a stupidly dangerous idea, but something annoys me about the fact that the ingredient for heat is already there yet we suffer from cool down.. 

[PureSilver]

The smart idea would be to use a liquid ignition system like Tippmann's Propane Enhanced Performance ('PEP') guns. Those used a 9v battery, and a small coil and spark plug to ignite propane, which came from normal disposable cylinders that you just screwed in the back. As far as I know, there weren't solenoids or anything like that to measure the gas; I would guess it was an inherently self-limiting system (much like I want BCRS to be) that vented excess pressure to achieve consistency. Bluntly speaking, it was a f***ing brilliant idea:

• You got fifty thousand shots from one 16oz (Coleman-size) cylinder (sixty times what you'd get from a CO₂ cylinder of similar size).
• A 16oz propane cylinder is about £8-9 if bought individually - i.e., less than a 570ml can of 'green gas' (propane) from which your average GBBr would be lucky to get 500 shots.
• Propane's vapour pressure at 20^oC is around 120psi; CO₂'s is around 800psi. Which would you rather have rupture?

The C3 never caught on - a criminal waste, in my opinion - because Tippmann was too committed to its CO₂ guns, and uncertain about company liability for imbeciles firing off a few thousand rounds rapidly and overheating the gun, so they made it pump action, which didn't have the rate of fire most paintballers wanted.

 

The first person that adapts the PEP system to airsoft to make a hard-recoiling AR-15 is going to make more money than he'll know what to do with. Fancy doing that instead, blobface?

[blobface]

....The C3 never caught on ...

 

Oh my god!.. OH MY GOD. Never knew something like that even existed... this would be so popular in all cold countries... I'd imagine it's still possible for it to be magazine fed (gas wise)? Gas tank wouldn't have to be so big anymore for more BB space... OH MY GOD, wait, pm. 

[scorch]

If its combustion fired, isn't that a firearm?

[blobface]

If its combustion fired, isn't that a firearm?

 

Yeah I was wondering about that as well... but apparently not, I suppose if it was the Tippmann C3 would have been illegal.. which evidently it wasn't... from my understanding of UK's classification of firearm, they didn't really seem to mention much about methods of propulsion, the various section, i.e. shotgun license... sec 1 ... sec 5... are to do with caliber and weapon length as well as whether it's manual / semi / auto etc... and as far air weapons the limit is at 8J before being a sec 1 firearm (even though a 20J air rifle is powered the same way as a 5J air rifle)... so if the system fires at airsoft site friendly 1 - 1.2J... I can't find any strong evidence that screams out to me saying that it's illegal.. but I'm no expert, so please correct me if I'm wrong so I don't end up on more watch lists. 

[sir naggedalot]

If its combustion fired, isn't that a firearm?

 

The system works like a nail gun,the gasses produced from combustion drive a piston,not a projectile...?

 

EDIT:Wrong,uses the gasses from combustion to directly propel the projectile.....!

 

I take it PEP's we sold in the uk?

[PureSilver]

If its combustion fired, isn't that a firearm?

 

Like blobface says, I don't think it's a firearm. The definition of a firearm is found in section 57 of the 1968 Act:

 

57 Interpretation.

(1) In this Act, the expression “firearm” means a lethal barrelled weapon of any description from which any shot, bullet or other missile can be discharged and includes—

(a) any prohibited weapon, whether it is such a lethal weapon as aforesaid or not; and

(b ) any component part of such a lethal or prohibited weapon; and

© any accessory to any such weapon designed or adapted to diminish the noise or flash caused by firing the weapon;

 

and so much of section 1 of this Act as excludes any description of firearm from the category of firearms to which that section applies shall be construed as also excluding component parts of, and accessories to, firearms of that description.

 

 

There is no mention of methods of propulsion in the Act insofar as I am aware. That's why airguns are firearms even though no combustion takes place; what separates them from firearms in terms of regulation is not the fact that they use compressed air but an exception in s. 1(3)(b ) specifically tailored to them. What would stop a PEP gun being a firearm in the English sense would be an absence of lethality (the same thing that stops other airsoft guns from being air guns, and thus firearms).

 

I'm 95% sure one of these could be built to satisfy the law, particularly as it would be completely different to a real gun internally and thus wouldn't contravene any of the rules concerning easy conversion.

 

[EDIT]

 

The system works like a nail gun,the gasses produced from combustion drive a piston,not a projectile...

 

I take it PEP's we sold in the uk?

 

No, I'm pretty sure the PEPs never made it out of the USDM. Tippmann are an American company, and it wasn't a commercially successful gun. Also, I'm pretty sure that it makes no difference whether the combustion drives the projectile directly or indirectly (e.g., via a piston).[/EDIT]

[viallet]

The propane canister used was a small green can we typically find everywhere for camping stoves, etc.  Apparently it will light at about 6% concentration so it basically dispensed into a little ported expansion chamber near the end of the barrel.  When the switch was actuated a solenoid valve intermittently allowed propane to flow down a tube to the combustion "area/chamber" where a spark generator would light it if the concentration was correct.  A friend works in refrigeration systems built the mechanism for us.  He built in a few "one way valves" for safety to prevent back flow of the gas.  Confined in a tight space it still froze up quickly and defeated us.  We weren't mobile at all with a car battery and propane can attached in the "ammo chute" to an ammo crate.

 

The Tippman idea is a great one.