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Armalite AR10 A4F build.......

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Replied by LebbenB on topic Armalite AR10 A4F build.......

Any issues with powder run out with the 14.5?
RLTW
10 years 2 weeks ago #36843

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Replied by faawrenchbndr on topic Armalite AR10 A4F build.......

Not familiar with that term,..........?
As in excessive muzzle flash?
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10 years 2 weeks ago #36844

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Replied by OleCowboy on topic Armalite AR10 A4F build.......

White man have STRONG medicine... :twothumbs:
10 years 2 weeks ago #36847

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Replied by LebbenB on topic Armalite AR10 A4F build.......

That's part of it. If the barrel is too short, the powder charge will not ignite completely while the projectile is still in the bore. This results in a larger muzzle blast and lower muzzle velocity of the projectile. It's also referred to as powder burn out. IIRC, the burnout rate for .308 is 15-16 inches, depending on the powder. I'm at work so I don't have access to my hard copy references.

If you have a chrony, I'd be interested in seeing what sort of MVs you're getting from it.
RLTW
Last edit: 10 years 2 weeks ago by LebbenB.
10 years 2 weeks ago #36850

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Replied by faawrenchbndr on topic Armalite AR10 A4F build.......

Do not have a crono available to check this barrel. Last short barrel, using m 118lr was clocking right at 2460.

My actual plan is to shorten the rifle length gas system, 18" barrel to 16"
Amazing shooters!
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Last edit: 10 years 2 weeks ago by faawrenchbndr.
10 years 2 weeks ago #36852

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Replied by LebbenB on topic Armalite AR10 A4F build.......

Interesting move. The trend has been to lengthen the gas system on shorter barrels. What's the gas port size going to be?
RLTW
10 years 2 weeks ago #36862

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Replied by faawrenchbndr on topic Armalite AR10 A4F build.......

I'm not sure what LMT is using for a port size. I have no plans to open it up.
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10 years 2 weeks ago #36877

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Replied by LebbenB on topic Armalite AR10 A4F build.......

If you shorten the gas system, you have to tighten up the gas port diameter. If you keep the port diameter the same size, you over-gas the gun substantially (Same volume of gas moving a shorter distance means it gets to the BCG faster and acts on it with more force.) which leads to premature wear and tear on the bolt as well as to issues like bolt bounce and rocketing.
RLTW
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10 years 2 weeks ago #36913

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Replied by OleCowboy on topic Armalite AR10 A4F build.......

Just wonder if you know how that is computed or do they use a table?

I would think there would be some standardization on that??????


.308 x bbl length / time of high tide = length of gas tube if gas port is ____?
10 years 2 weeks ago #36917

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Replied by faawrenchbndr on topic Armalite AR10 A4F build.......


Have no plans to mod the gas system at all. There are a lot of these rifle length gassed 16" barrels being used with standard size gas ports. None exhibit bolt bounce issues either
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10 years 2 weeks ago #36929

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