Why a belt-fed squad automatic?

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RyanM

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Something that's been puzzling me for awhile. Why does the US Army use a belt-fed machinegun as a squad automatic?

My best guess is that it's just tradition, an extension of the "horse cannon" concept, in which a team of men can move a tripod-mounted machine gun from place to place on a battlefield. Someone liked that concept so much, they decided to make it so that one guy could lug around a 30 pound LMG with a bipod, and a bunch of other guys in the squad could carry ammo.

I really cannot see any concrete benefit to using a belt fed system, though. You end up with a gun that's bulkier, heavier, more complex, and inherently less reliable. You have to train soldiers a different manual of arms. Because the soldier has to actually lug around the gun and ammo, there's a limit to how much ammo can be in the gun at one time. From what I've heard, in Vietnam the standard M-60 belt length was 50 rounds. Right now, most soldiers prefer the 100 round nylon pouches, since they're much lighter than the 200 round ones.

Sustained rate of fire? The time it takes to reload means there won't be a whole lot of difference there. Pull back operating handle, open cover, remove pouch, attach new pouch, tilt gun to the right, position first round, close cover.

If the cyclic rates of fire between a mag fed and belt fed gun were equal, let's say 10 rounds per second, and it takes 2 seconds to swap a mag, 5 seconds to change belts, that gives an actual maximum rate of fire of 360 rounds per minute for a gun which uses 30 round mags, compared to 400 rounds per minute for a gun that uses 100 round belts. Not a heck of a lot when the belt fed gun weighs twice as much.

Ammo weight, once again there's little difference. 300 rounds in magazines weighs 10.7 pounds. 300 rounds in linked, pouched ammo weighs about 10.0 pounds.

About the only benefit of the M249 in particular is it fires from the open bolt so it cools faster, and has a higher rate of fire. And the weight might help with the recoil (inasmuch as 5.56mm has recoil, even in full auto). But what's the benefit over a magazine-fed M16-based LMG, which fires from an open bolt at a higher cyclic rate, uses larger capacity magazines (maybe decent quality drums), and has some weight added (steel receivers would be a good start)?

It seems like the Russians came to the same conclusion as me, as they saw fit to replace the RPD with the RPK in the squad automatic role (and the PKM for their all-around LMG). So why does the US Army use the M249 as a squad auto?

Belt fed makes perfect sense if you can actually park your butt somewhere for a few minutes, mount the gun on a tripod, and link a few cans worth of ammo together. But not if you have to get up and run at a moment's notice.
 
Have you ever fired a belt-fed LMG? I've fired both the M60 and the M249. They are not nearly as bad as you make them out to be. Belt feed works great, actually, and allows much more practical carry and immediate use of large (>100's) quantities of ammo than magazines or drums do. It does require some maintenance and skill, but it's nothing any moderately skilled american 18 yo can't manage (it might perhaps be too much for conscripts in countries that don't have running water or electricity).
 
You have to police up your magazines before you get up and move. Magazines are more unreliable then belts. You have another component to fail.

From what I've heard, in Vietnam the standard M-60 belt length was 50 rounds.
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100 rounds but many machine gunners used a short teaser belt when moving.

Right now, most soldiers prefer the 100 round nylon pouches, since they're much lighter than the 200 round ones.
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The nylon bags are preferred because the plastic boxes that M249 ammo comes in are junk and they tend to fall off the weapon.

Ammo weight, once again there's little difference. 300 rounds in magazines weighs 10.7 pounds. 300 rounds in linked, pouched ammo weighs about 10.0 pounds.
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It's not weight, it's cube. 300 rounds of linked ammo takes up less space then 10 30 round magazines.

If the cyclic rates of fire between a mag fed and belt fed gun were equal, let's say 10 rounds per second, and it takes 2 seconds to swap a mag, 5 seconds to change belts, that gives an actual maximum rate of fire of 360 rounds per minute for a gun which uses 30 round mags, compared to 400 rounds per minute for a gun that uses 100 round belts. Not a heck of a lot when the belt fed gun weighs twice as much.
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Your 8 or 9 pound magazine fed weapon will be overheated to the point of failure after a few iterations of that firing sequence. I don't care if it's magazine fed or belt fed, it has to have a certain amount of mass to absorb all that heat.

About the only benefit of the M249 in particular is it fires from the open bolt so it cools faster, and has a higher rate of fire. And the weight might help with the recoil (inasmuch as 5.56mm has recoil, even in full auto). But what's the benefit over a magazine-fed M16-based LMG, which fires from an open bolt at a higher cyclic rate, uses larger capacity magazines (maybe decent quality drums), and has some weight added (steel receivers would be a good start)?
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The US military has experimented with your idea since the 1960s. Colt made the CAR-15 HBAR which was an M16/XM16E1 with a heavy barrel and a modified BAR bipod. Model 606B which was burst fire and had an adapter near the muzzle for the M2 rifle bipod. Later they played with the Colt's HBAR M16 which fires from the open bolt has a lightened gas/front sight block a new squared off hand guard and an M60 bipod. None of these versions beat the M249 in testing.

Jeff
 
Actually, the "traditional" squad auto was magazine fed (BAR, BREN) until the German idea of the general purpose gun caught on.

In addition to the comments above, I might also note the logistics aspect. If the squad auto is magazine fed, that is just so many more magazines that have to be manufactured, transported, stored, and carried forward. 100 rounds in a belt is a fairly small package and doesn't weigh much more than the ammo itself. 100 rounds in magazines (assume 20 rd magazines) is a larger package and weighs considerably more than the ammo alone.

Plus the gunner has to keep changing magazines, a chore in itself and dangerous since the gun is out of action during magazine change.

Jim
 
Sounds like the LWRC IAR fills your request IAR
We'll see if it's well received. I wouldn't want to be swapping mags every couple of seconds when you are supposed to be keeping heads down. Under ideal conditions you could probably swap them in 2 seconds but who knows.
I doubt the IAR would win in a head to head competition with the 249 when it comes to laying down large volumes of lead.
 
I just got back from spending 4 days on the range up at Ft. Drum where we had about 80 people to go thru ammo intended for an entire batalion, 5.56mm, 9mm, 40mm, and 12 guage.

I don't remember the specifics but it was on the order of over 70,000 rounds.

we had numerous weapon failures, M16-A2s, MK19s, M249s and one M203. We had a number of individuals conducting mag dumps firing in burst mode with their M16s, to the point where slings began to melt off of the rifles and handguards began to smoke. One rifle heated up so much that the mounting equipment for the 203 melted and it twisted sideways in the soldier's hands. The finish on M249 barrels were cooked off, as well as gas regulators developed stress fractures in them. All this from hours of almost continous cyclic fire. I personally didn't subject my rifle to that kind of tourture, plus I had already cleaned it from qualing and didn't want to clean it again.

We also experienced a number of rifles doubling and some slamfires, or possibly rounds cooking off. I also learned that you can't really aim a MK19 to its max range and it takes the rounds about 10 seconds to reach out that far, and an APC looks really really small to the naked eye way out there.

Personally I don't like the M249 as is, they should get rid of the magwell on it, that would remove some of the nooks and cranys that gunk collects in and makes cleaning for COMET inspections such a PITA.
 
The nylon bags are preferred because the plastic boxes that M249 ammo comes in are junk and they tend to fall off the weapon.
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Not over the boxes, but over the 200 round nylon "nutsacks." The original 200 round nylon ones also allowed the belt to get tangled, but that may have been fixed by now. In any case, what I've been hearing, anyway, is the 100 round nylon ones are preferred because they're lighter.

Your 8 or 9 pound magazine fed weapon will be overheated to the point of failure after a few iterations of that firing sequence. I don't care if it's magazine fed or belt fed, it has to have a certain amount of mass to absorb all that heat.
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So make it heavier. Making things heavier is never a problem, unless they also need to fly. :p

The US military has experimented with your idea since the 1960s. Colt made the CAR-15 HBAR which was an M16/XM16E1 with a heavy barrel and a modified BAR bipod. Model 606B which was burst fire and had an adapter near the muzzle for the M2 rifle bipod. Later they played with the Colt's HBAR M16 which fires from the open bolt has a lightened gas/front sight block a new squared off hand guard and an M60 bipod. None of these versions beat the M249 in testing.
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But what exactly were the criteria? Obviously, the Ruskies found some kind of benefit of having a closed-bolt, mag fed squad auto, or they would have just used the PKM for everything.

------------------------

In addition to the comments above, I might also note the logistics aspect. If the squad auto is magazine fed, that is just so many more magazines that have to be manufactured, transported, stored, and carried forward. 100 rounds in a belt is a fairly small package and doesn't weigh much more than the ammo itself. 100 rounds in magazines (assume 20 rd magazines) is a larger package and weighs considerably more than the ammo alone.
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On the other hand, having no belt-fed 5.56 means that they could shut down an entire factory (or more likely several) devoted to making 5.56 links and linking ammo together, and magazines could be used for either weapon platform.

Bulk, there is more for magazines, but weight difference, especially if you include the pouch, like I said is fairly minimal. 12 ounces per 300 rounds.

Plus the gunner has to keep changing magazines, a chore in itself and dangerous since the gun is out of action during magazine change.
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Belts let you shoot longer, but they also take longer to reload, unless you're able to link a new belt onto the old one. Which is no mean feat, if you're in a hurry.

And what about drum mags? If C-mags were any good at all, you'd have the same time between reloads as a 100 round belt. Basically would be sacrificing weight, bulk, cost, and reliability for reload speed, though, which may not be a good trade-off.
 
I don't remember the specifics but it was on the order of over 70,000 rounds.

we had numerous weapon failures, M16-A2s, MK19s, M249s and one M203. We had a number of individuals conducting mag dumps firing in burst mode with their M16s, to the point where slings began to melt off of the rifles and handguards began to smoke. One rifle heated up so much that the mounting equipment for the 203 melted and it twisted sideways in the soldier's hands. The finish on M249 barrels were cooked off, as well as gas regulators developed stress fractures in them. All this from hours of almost continous cyclic fire. I personally didn't subject my rifle to that kind of tourture, plus I had already cleaned it from qualing and didn't want to clean it again.
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What was the point of all this abuse? It's not news to me that full auto weapons overheat after enough sustained firing. This sounds like some guard unit that wasn't disciplined in the least and basically had a beer n'guns weekend. I mean no offense if that's not the case.

Belts let you shoot longer, but they also take longer to reload, unless you're able to link a new belt onto the old one. Which is no mean feat, if you're in a hurry.
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On the M60 a new belt can be loaded in about 3 seconds if you have it ready. Definitely no issue if you have an assistant, which would be the norm on a M60. I have far less time on the M249 but I don't think it takes much if any longer (although the SAW gunner usually doesn't have a helper).

But what exactly were the criteria? Obviously, the Ruskies found some kind of benefit of having a closed-bolt, mag fed squad auto, or they would have just used the PKM for everything.
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The "Ruskies" had different doctrine and a much lower standard of recruit and training. The RPK is basically a heavy barrel AK. So training and operation is very simple and no real extra training is needed. It is a decent gun, but not near the equal of the US guns with belt feed and changeable barrels. Serious LMG's have changeable barrels, period. (The easier the change the more serious - and the early version M60 is weak in this respect because of the awkward changing procedure.)

Ryan, what's your point here?
 
Belt-fed, mag-fed, OMG

This is a headache.
I'm convinced that if you solved all the problems with high-cap mags, they could replace belts.
But no one has solved them yet. Which leads me to believe it may take a technological break-through to do so.
Plastics help reduce the weight of big mags, which is a bonus. Those magazines could possibly be stored in the same space as a nylon belt pouch.
Theoretically.
Standard rifle magazines will not do, as was proven with the BAR and BREN. They just lack to capacity for a real gunner.
Machine guns are heavy not because they're fed from a belt (the Stoner LMG weighs ten pounds and is belt-fed) but because they need extra weight to absorb recoil and heat. The weight that is used to absorb recoil can be replaced with a constant-recoil system, but the weight needed in the barrel to absorb heat cannot be replaced with current technology. So the LMG's minimum weight is about 10 pounds.
As for this statement:
So make it heavier. Making things heavier is never a problem, unless they also need to fly.
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Tell that to the guy who has to hump it all.
Weight is a real issue.
If someone could solve all the problems of magazines, then they might be better than belts. No one has done that, and I don't think anyone is working on the problem right now.
And, hey, if you used all that effort to solve the problems of belts, you'd probably still be better than the super-duper big magazines.
Belts are here to stay. Especially with the LSAT looking into plastic links. Those could prove tough, light, durable and more reliable.
We won't see the end of belts anytime soon.
 
One problem with most magazines be it stick or drum is the spring.

You don't have that problem with a belt fed gun.

It also doesn't take nearly as long to load a new belt as some have implied.
 
When I was assigned to JSA in Korea to run counter infiltration patrols in the DMZ, I was given a choice on what to carry. The choices were the M16A2, the M203 amd the M249 SAW. I knew all three like the back of my hand. I chose the M249 SAW. If I'm going to be sharing the woods with North Korean Special Forces, I want to have 600 rounds of fun and excitement to party with:evil:.

Flip.
 
What I'd like to see for a "static emplacement" weapon would be a mechanical feed system, where one could feed a hopper, and they ammo would self-align on the way to the chamber - kinda like what Dillon uses for its hoppers...
 
RyanM, please be kind and share us your extensive experiences in military and with different military arms, including mag-fed and belt-fed automatics. So that we can see your authority on the issue.
 
The reason we had so much ammo and had to burn thru it the way we did is this.

The ammo was asked for during the last fiscal year, which happened to start Oct. '06 back when the whole state was going thru a reorg. and those in the ammo ordering dept were used to dealing with infantry units. Next like I said the ammo was intended for a batalion sized element but was up to a single company, half of one really to finish up the ammo for this fiscal year.

Now we had to use up all the ammo for the fiscal year otherwise when they go to ask for more ammo the higher ups will say you didn't use all the ammo we gave you last time so therefor you didn't need all of it so next time we're giving you less.

There were also time constraints, too much ammo and not enough time. We had additional training planned, reflex fire, transitional fire and all that but situations arose that prevented that.

I'm sure most will agree that shooting heavy volumes of fire is fun in small batches but it shortly becomes a chore, something you don't really want to do but must anyways. I remember having to do it once before with M2s, I personally fired over a thousand rounds in a very short time period.

And I do take offence slightly to your post, over half of the unit, including myself, are combat vets who've been back less than a year.
 
Having fired the 249, I know it offers significant suppressive fire advantages over the M4.

It's necessary to understand the role of the M4 vs. the 249. The 249 offers suppressive fire at high sustainable rates. The M4 does not.

It's fully automatic and designated for its' role. The M4 is semi-automatic or 3 round burst. In the intersest of conserving ammo and making Soldiers make each shot count and accountable, it's necessary for the M4 to be designed that way, for better or worse.

If you have M4s that are fully automatic, you will be changing mags and burning through ammo too quickly. The weapon will over heat and/or you will simply exhaust your ammo supply. That's why SAW gunners have significantly more ammo.

Belts are necessary and effective. They are lighter and more compact and less expensive than mags. Storing 600 rounds in magazines requires 20 magazines (an extra weight of 5 pounds and cost of $200). Firing 600 rounds from a belt requires 5 belt changes (on a 100 round belt). Firing 600 rounds from magazines requires 19 magazine changes. If you have a crew firing the SAW, someone is there to load the belt for the gunner so it takes almost no interuption in rate of fire. Either way, a belt change is as simple and fast as a magazine change.

And the SAW can accept M4 magazines and can also be mounted on vehicles or other locations as an effective weapon.

Overall, the SAW is a great squat weapon.
 
Having fired several M249s in the Army, Ive never had an issue with any of the aforementioned situations, even the overheating thing.

I have to agree with Medusa: What are your qualifications for all this? Its just that we as internet forums get so innundated with "armchair commandoes" that never fired a weapon badmouthing it and not knowing the real situations.

Plastic box falling off? Never had that issue and we ran around with the flargin thing. Magazine fed? Well, I did get to horse around with the adapter that allowed the M16 mag use with the 249, seemed to slow the rate of fire, not to mention having to change mags darn near every trigger pull. It is a heavy piece of weapon, however, what isnt when you are humping a pack and other junk :D. Want something heavy to complain about? Try lugging the M240 Bravo around for a 5 mile run on top of PT with a drill sergeant yelling at you for not cleaning it correctly :D.
 
Cost is also doubtless a big concern; even if you COULD design a high-capacity, reliable magazine that wasn't so bulky that no-one would want to carry the bloody things, once they were in the field, they would be treated as "expendable stores", unless you ordered soldiers under fire to pick up their empty mags and refill them. That's not a big problem for rifle mags, since most grunts WANT all the spare mags they can get their hands on, but if it came to something that would have to be as big, heavy, and expensive as a SAW mag, most soldiers I know would probably prefer to "lose" them. With belts (at least with disintegrating-link belts), it's a non-issue, since the whole package is expendable.
 
When I carried the 249 people thougt I was nuts. Why do you want to pack that bulky heavy thing that jabs you all the time.

I said because while your changing mags I will still be thumping away keeping the commies heads down untill you get back in the fight.

Is the 249 perfect? No but neither is the most expensive weapon in the US Army the Patriot Missle. Did you know that it has a bug in the program that allowed it to lose .1 sec every day. This threw off the targeting system and all them spectaculer kills you seen in the Gulf War were really a guy in the control both hitting the self destruct button. The 240 is not perfect the M2 is not perfect neither is any weapon system. But the 249 for what it is designed to do does it better than any other weapon system out there for now. Soon the whole ammunition argument will be null and void when they come out with caseless ammo with biodegradable plastic links that act as a feterlizer.

Battle chimp hit it right. That 240B is a very good weapon system but it sucks to lug that puppy around. I used mag fire once on my 249 and it was worthless when a weapon system fires as fast as the 249 does a mag can't keep up.

I have quaified on just about everthing in the arms room of my unit while in the Army. I had my pick of what to pack and when I could not have the Mk-19 and the SAW I took the SAW. I will put up with belts and weight to know that I am packing firepower. My plastic boxes never fell off and it mine didn't then I doubt anyones did. Why? Well my SAW rode around on the side of my D7 Dozer while digging implacements for M1 tanks.
 
and it was worthless when a weapon system fires as fast as the 249 does a mag can't keep up.
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Hey, cpttango30! Does this bring back memories?
Buuuurrrrrrrp click (cycle bolt) burrrrrrrrrrrp click (cycle bolt)
new mag
Bur click (cycle bolt, curse) burrrrrrrrrp click (curse more, hold up hand for RO to come over) :D
 
Kind of funny. I ask why something is, and explain why I'm asking.

The people who are actually qualified to answer, give a straight answer.

The people who doubtlessly are not, ask how I could possibly be qualified to ask a question. After all, you have to know enough to not ask in the first place, to get a question-asking license.

Welcome to the internet.
 
Having carried the Steyr Aug and the Minimi in my time, one aspect that slightly plays on my mind is that both have 20 inch barrels and therefore the terminal ballistics of both are going to be very similar. The benefit of the Minimi is of course capacity, higher cyclic rate and sustained fire, but it still isn't any more powerful, shot for shot, over any 20inch barrel, 5.56 select fire rifle.

So I've often thought that if it were upto me ( and maybe it's a good thing that it isn't ) instead of equipping an Australian infantary section (squad) of 9 men with two Minimis and 7 AUGs, another option would be 5 standard config AUGs and 4 HBAR AUGs with bipods and 42 round magazines.

You still have the quick change barrel option due to the design of the AUG, logistics would be eased, as would training. Carriage of the HBAR AUG is obviously going to be easier and fire and movement would definately be easier. 4 light support weapons would allow for a slighlty increased array of tactical options in comparison to 2 light support weapons. You also wouldn't have to worry about 'giving the position away' of the Minimi/light support weapon for perimeter defence on the basis of noise, at least not so much.
You also could utilise the HBAR AUGs in a designated Marksman type role as well.

However, even I realise that no rifle is going to be as robust as a belt fed machine gun, and even with 4 HBAR AUGs you may still not have the capacity for sustained fire required in certain situations.

Of course there is the option of equipping an Aus. section with 5 AUGs and 4 Para-Minimis...
Just a pity we don't use them outside of the tip of the spear...
 
Even though I have not fired either, I would have to say that the SAW has a MAJOR advantage over the magazine fed LMG. It has both higher capacity and better sustained fire capability. The open bolt allows it to cool a little and is designed for heavy firing. I am not a fan of sustained fire in a non-belt fed weapon.
 
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