The Ground Precautionary Message ACALA #97-031, from November 2006, clearly states that if an M4 barrel reaches just 737 degrees Celcius, the barrel will be weaked to the point where burst.
(3) BURST BARRELS RESULT WHEN THE WEAPONS ARE FIRED UNDER VERY EXTREME FIRING SCHEDULES AND THE BARREL TEMPERATURE EXCEEDS 1360 DEGREES FAHRENHEIT. WHEN THE BARREL REACHES THESE EXTREME TEMPERATURES, THE BARREL STEEL WEAKENS TO THE POINT THAT THE HIGH PRESSURE GASES BURST THROUGH THE SIDE OF THE BARREL APPROXIMATELY 4 INCHES IN FRONT OF THE CHAMBER. THIS CONDITION CAN RESULT IN SERIOUS INJURY.
You are not going to see an M4 barrel white hot because by that point it would have exploded!
The AP also infers that the M4 Carbine is designed to handle a high rate of fire
The high rate of fire appears to have put a number of weapons out of commission, even though the guns are tested and built to operate in extreme conditions.
This is also not true. From the Ground Precautionary Message[^1]:
(B) FIRING 140 ROUNDS, RAPIDLY AND CONTINUOUSLY, WILL RAISE THE TEMPERATURE OF THE BARREL TO THE COOK-OFF POINT. AT THIS TEMPERATURE, ANY LIVE ROUND REMAINING IN THE CHAMBER FOR ANY REASON MAY COOK-OFF (DETONATE) IN AS SHORT A PERIOD AS 10 SECONDS.
...
(D) SUSTAINED RATE OF FIRE FOR THE M16 SERIES RIFLES AND M4 SERIES CARBINES IS 12-15 ROUNDS PER MINUTE. THIS IS THE ACTUAL RATE OF FIRE THAT A WEAPON CAN CONTINUE TO BE FIRED FOR AN Indefinite LENGTH OF TIME WITHOUT SERIOUS OVERHEATING.
I've gotta say, this crap is not encouraging my confidence in this weapon for the troops.
3 comments:
Like TheFirearmBlogger said - "... I cannot think of any current weapon in the M4 class that can sustain continuous fire. To make such a weapon it would need to have a heavy quick change barrel and maybe also include a heat sink. I doubt any soldiers will want to trade in their M4 for a heavy automatic rifle."
The problem here is physics, not the M4. Nothing portable enough to make a good assault rifle is going to do indefinite suppressing fire without severe issues, at least not with today's metallurgy.
Maybe we should make more water-cooler M1917s for firebases...
Ditto. We stopped carrying BARs for a reason. It might not have been a good reason, but they at least thought about it.
The M4s aren't for things like suppression fire. They are for aimed shots. The SAWs are for sustained fire (and there are reports that they were having trouble with them, too, which is an issue, because that is supposed to be its role.)
Also, you can put that many rounds through a BAR, but you are going to shoot the barrel out pretty quickly. Even a BAR is designed for aimed fire and a restrained firing cycle. Anything short of a medium or heavy machine gun that is getting that much lead shoved through it is going to have problems with barrel weakening and cookoff.
You do have to wonder if, for a fixed base like that in a very dangerous place, something like the 1917 wouldn't be a good idea. It's big and heavy; it'll also keep firing as long as there's ammo and you can keep liquid in the cooling jacket.
A GPMG with an attachable cooling jacket or something similar to cool it?
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