What's wrong with belt-fed AR15s?

From what I understand, they can be picky and finicky.

I forget what YouTube channel runs one, but I think it had a pretty extensive break in process.

Plus, to beef one up for sustainable fire that the military needs, you end up with something exactly like a 249... But at least the 249 was built from the ground up for that as opposed to retrofitting.


But... If someone could make one be reliable and beefy, with factors making improvements, it would make sense logistically. If we could afford to refit.

A belt-fed semi-auto would be silly. I can see no real purpose or benefit to it.

Every so often these things show up. I've seen them in 5.56 and 9mm, but for sheer WTH, you gotta see this.
As a young man, I dated an M60 that had to be older than I was. The novelty of those things tends to wear off after a while.

I can think of two reasons.

As I recall, the barrels on M16 (the military one) and the one civilian type (a clone of the Colt AR 15) are rather thin. They heat up fast. They get too hot to touch after twenty rounds (magazine full). Most US GI belts for ground type weapons are one hundred rounds. Firing a belt of 100 rounds would heat up the barrel more than the expected fives times as much. The leade part of the barrel would be burnt out rather quickly. Unless specially designed and altered, the rifles do not have quick replace barrel.

The M16 - and variants - are an individual's issue rifle. With a belt feed, it would be too awkward to carry as such. Such a device would be more of a squad weapon and of limited use. (See above.)

I had the chance of shooting one before. Pretty neat, but it was still in semi-auto, so...and this was pre bump stocks. Neat idea, no practical use though except to burn through ammo...Now, the Barrett, that is a whole nother level of fun there, especially in semi-auto.

But what happens next? The squirrels counter with arty, you have to go get little F\A18 drones for an airstrike. The squirrels might have to get to work on the Manhattan Project, or maybe Buffalo to scale it down...

Thanks The Exile. Most fun I've had all day.

I think I see. Sometimes these things have to have ALL the pieces to make sense. You need to add this to a registered FA lower and add the belt fed .22lr upper...

DocRock said:

A belt-fed semi-auto would be silly. I can see no real purpose or benefit to it.

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The one benefit.
Oh yeah? Well I have a belt feed AR...
Down sides are retrofitting an otherwise decent platform into an unreliable range toy.

The Exile said:

. . . if a belt-fed AR15 was a good idea why didn't the military make one?

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In some sense, they did, and named it the M249. The lightest/smallest practical 5.56 machine gun.

I think the mass and barrel weight gap between the M16/M4 and the M249 is the answer to "why no belt fed M4?"

The barrel can be beefed up like the SOCOM profile, but the weak link would be the gas tube. I have seen plenty of melted and blown gas tubes over the years. A gas piston system would be better, as pointed out the M249/Ultimax/Negev are purpose built from the ground up.

The AR15 platform was never intended to be a sustained fire full auto platform like the SAW. Run one with a belt at capacities well beyond 30 rounds and you’ll wash that barrel out in no time at all. The barrel throat will erode to the point that accuracy will become non-existent. But then I suppose anyone wanting to run one of these with a belt may not care all that much about accuracy...the “Water Hose” concept of marksmanship lives on. So for all you Rambo and Terminator fans out there, have at it. After all it works well in the movies!

Heck, a lot of Marines have gone to the M27, a box magazine gun replacing the M249.

The M249 is essentially a belt fed AR15, as far as weight and length go. It can even use AR magazines. The issue is with the gas system. The M249 wasn't reliable with the DI from the AR, which is why it is an open bolt long stroke piston action instead.

rodinal220 said:

. . . the weak link would be the gas tube. I have seen plenty of melted and blown gas tubes over the years. . .

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I'm interested to know what one has to do to get near blowing a gas tube. Is this a high round count thing, or and extended mag(s) dump thing?

SharpDog said:

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there aren't enough like buttons

Personally I always thought that the Stoner 63 was the closest thing I have ever seen to a belt fed full auto ar-15.

zdc1775 said:

Personally I always thought that the Stoner 63 was the closest thing I have ever seen to a belt fed full auto ar-15.

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Me too but they were sort of a "limited edition" when it came to use.
I sort of remember that the SEALs had them..?

The Exile said:

after all if a belt-fed AR15 was a good idea why didn't the military make one?

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The US Government doesn't make rifles... they buy them from the lowest bidder.

Ares Defense made a product called the Shrike which was a belt-fed upper. IIRC, the army did some field tests... and nothing further.

herrwalther said:

The M249... can even use AR magazines.

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Every time I tried this it worked out less than perfectly, though...

Shanghai McCoy said:

Me too but they were sort of a "limited edition" when it came to use.
I sort of remember that the SEALs had them..?

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Yeah the SEALs had them, the one I saw was at the Naval Special Warfare Museum, and I believe that the Marine Corps tested a version of it in the late 60's or early 70's. If I am remembering correctly they made around 4,00 of them but in field use it proved to be too fragile for general issue.

My first thought was to ask "Who has to load the belts?" my second question is .. and just what did they do to deserve that job...

One thing is certain - almost every possible improvement has been thought of - a few of them actually worked - but they still had to be practical, usable - and get past some very skeptical folks in the procurement end of things...

Always fun thinking about it though...