Primary concern under full auto fire

[FA sear]

What is the primary concern under full auto fire? Warped barrels are what I have always been told is the primary concern under full auto fire, but I have heard a couple people say that gas tubes melting are the primary issue.

I have always understood gas tubes melting is a secondary issue to barrels warping. Any of you veterans out there care to explain the details?

[FA sear]

Never mind. I had my own question answered.

For those of you who may have been curious about what the answer was.

A good quality gas tube isn't going to melt under full-auto fire circumstances.

It could be possible with a cheap crappy gas tube.

Or a gas tube with a manufacturing flaw.

Alot of continuous rounds would have to be fired, even for that to come close to happening.

More likely that the barrel would have problems first.

Sometimes you may see them droop a bit, or deform some, but not melt altogether.

The company I work for has done exhaustive barrel testing under continuous full auto conditions, and the barrels always failed before the gas tubes in our tests. I have data on about a dozen barrels which showed up to 960 rounds fired in some cases, with total barrel meltdown, and handguards on fire, and the gas tube was still intact.

The purpose for a piston system is not because of gas tube melting problems.

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MGI Military Factory Sales Manager

[Zebb]

I'm glad we got that sorted out then..

[spearhead]

very interesting, thanks for that

[RooK]

John Browning fired his 1919 for the military in a trial and had a huge amount of ammo attached to it, he just kept shooting. By the time he was out of ammo, the barrel was a bright red and bullets were little more than lead smears on the target, but the gun still worked.

As far as modern small arms, I'd be more worried about if what I'm holding is on fire/melting than the gas tube or barrel. You'll probably not be able to hold the gun any longer for it to be of use before a part fails from continuous fire.

[FA sear]

I'm glad we got that sorted out then..

←

I just knew someone would say that.

I got some more tech data on this matter. Here is the info.

In our barrel testing, in which numerous barrels were subjected to continuous full-auto firing to destruction, pausing only to change 30-round magazines, and with thermal sensors placed at every one-inch segment of each barrel during the test, the heavy barrels fared the best.

This is due to the greater mass of the barrel, and the stiffness associated with the larger diameter of the heavy barrels.

The highest temperatures were recorded between the section that was 2" forward of the chamber, to about 7" forward of the chamber. Basically, the area under the handguards. The chamber itself is not the hottest portion of the barrel under stress.

In most cases, the lighter barrels began to cook-off before 200 rounds were reached.

Heavier barrels began cooking-off later, around 220-240 rounds fired.

Destruction occured between 500 rounds and 960 rounds, depending on the type of barrel.

Temperatures over 1500 degrees were reached in some cases.

This was at room temps.

In the tests conducted at 155 degrees F, simulating desert conditions, the round counts to cook-off were about half the number of rounds that were possible at room temps, and only about 4 mags could be dumped until cookoffs occurred.

Interestingly, in all of these tests, there was not even one failure of a gas tube.

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MGI Military Factory Sales Manager

@RooK

You are right that you probably will not be able to hold the gun. A lot of people at the mg shoot outs that participate in multiple beta mag dumps will often fire these guns from a bipod, or simply shot prone with support under the barrel.

Edited August 25, 2005 by jchung