NSWC testing on gas systems. CARBINE VS MID-LENGTH

[npena84]

So at the NDIA conference a study was revealed. That tested the reliability, durability, and accuracy (among others). Of the mid-length gas system vs the carbine length. It seems to confirm much of what is already known. With a couple of surprises throw in as well. Worth the read.

http://soldiersystems.net/2018/05/14...d-performance/

[Serious Account]

Very interesting. So it's been confirmed that midlength is indeed superior.

I wonder what gas port size are they using for the mid, and how well will it function with weaker/underpowered ammo + H2 buffer. Are they optimizing this for M855A1 only?

My guess is 14 in mid is likely to be a little more finicky with ammo than carbine gas.

[Mr. Goodtimes]

I’m curious how accuracy degradation started at a mere 7,000 rounds in the carbine length guns. That’s not very many rounds. Also the test is skewed in terms of barrel life as the gas system has nothing to do with that and the mid length barrels are hammer forged where as the carbine ones are not.


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[Coal Dragger]

Good read, although I wonder if the barrel accuracy life findings have more to do with cold hammer forging than where the gas port is located?

[Mr. Goodtimes]

Good read, although I wonder if the barrel accuracy life findings have more to do with cold hammer forging than where the gas port is located?

They definitely do, as gas port location has nothing to do with barrel life, however, I’m curious to know how they were only getting 7k rds is barrel life out of a regular barrel.


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[npena84]

Could the barrel degradation be the results of using EPR?

[alx01]

I’m curious how accuracy degradation started at a mere 7,000 rounds in the carbine length guns. That’s not very many rounds. Also the test is skewed in terms of barrel life as the gas system has nothing to do with that and the mid length barrels are hammer forged where as the carbine ones are not.


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Am I mistaken or did I read somewhere on m4c that COLT non-hammer forged barrels lasted over 60k rounds? I simply don't believe that regular COLT barrels degrade at 7k rounds. Maybe SBR's like MK18 at longer distances.

In my anecdotal experience, typically it's almost impossible to tell the accuracy degradation if doing groups at 100m. As barrels age they still tend to group well at 100-200m (even 250m). Once you start going to 400-600m range is when you can really tell the difference between a good barrel with 10k barrel rounds and a worn/bad barrel. Too many factors affect the barrel life in my opinion including cleaning schedule, production methods/materials, most importantly rate of fire the barrel has been through. This is true regardless whenever the barrel is CHF or not.

I find it a bit amusing that people think that CHF is always superior - its only better if process, materials, and treatment are suitable. Yet, there are millions upon millions of non-CHF barrels that perform fine. I suspect, in a regular use scenarios (mil or civ) it's impossible to tell the difference between the two types besides the markings.

Would I choose a CHF barrel over the regular one? In case of BCM, Noveske, DD, or other known manufacturer - probably yes. But I wouldn't be hell bent on it. By the same logic, I think it's always better to choose a regular barrel of a well known brand over CHF of questionable production.

[Bourne911]

That accuracy standard is pretty crap .

[Glock9mm1990]

This is interesting to say the least, but only 6000 rounds in a Colt barrel? That must be because of the M855A1 round.

[ABNAK]

Yeah I'm thinking M855A1 has something to do with that.

Also, how do you get a velocity difference at 100m? i.e. how is that impacted if the muzzle velocities are similar? Gun X MV is 2900fps. Gun Y MV is 2900 fps. Yet Gun X is going faster at 100m? How the hell does that happen using the same ammo?