reliability of carbine length gas systems v rifle

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11 years 8 months ago #17514 by sonogun
reliability of carbine length gas systems v rifle was created by sonogun
I plan on building an AR-15 using a Aero Lower and a Armalite SPR Mod 1 mid length upper with a stainless steel match barrel. Must I use a 16 inch barrel or will the mid length upper work with a 20 inch barrel? My second question concerns the reliability of the gas/bolt system in a carbine length set-up verses a full length. Is stress on the bolt, heat in the barrel, reliability, lifespan and feeding compromised in a carbine?

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11 years 8 months ago - 11 years 8 months ago #17525 by LebbenB
Replied by LebbenB on topic reliability of carbine length gas systems v rifle
Barrel length drives gas tube length. If you plan to use a 20" barrel, use a rifle length gas tube and a rifle length forend/FF sleeve/rail system. If you're wanting to re-barrel to a SS match barrel while re-using the gas system components and forend, then you're pretty much locked into a max length of 16". (Though a 14.5" SS with a mid-length gas system would be a great low cost alternative to a Noveske Afghan. Just sayin'...)

A carbine length gas system is harder on bolts. This is becasue the gas impulse impinging on the bolt is stronger due to the shorter length of travel the gas has in a shorter carbine-length gas tube. The increased strength of the gas impulse decreases the dwell time of the bolt, meaning it unlocks and starts it's reward travel before the case cools and contracts. This makes extraction harder and increases the shear force on the bolt lugs.

That said, a heavier carbine buffer - H, H1, H2 types - mitigates this and returns the dwell time to nominal levels becuse of the additional mass/weight the BCG has to push against IOT begin the extraction process. Hard extraction was the main reason the mid-length gas system was developed in the first place.

Good luck on your build.
Last edit: 11 years 8 months ago by LebbenB.

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11 years 8 months ago #17526 by Dabu
Replied by Dabu on topic reliability of carbine length gas systems v rifle
You might want to look into the gas piston systems for carbine rifles. They're a little heavier, but no hot gas goes back into chamber.

check out this cool video.

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11 years 8 months ago #17548 by Sharkey
Replied by Sharkey on topic reliability of carbine length gas systems v rifle

LebbenB wrote: Barrel length drives gas tube length. If you plan to use a 20" barrel, use a rifle length gas tube and a rifle length forend/FF sleeve/rail system. If you're wanting to re-barrel to a SS match barrel while re-using the gas system components and forend, then you're pretty much locked into a max length of 16". (Though a 14.5" SS with a mid-length gas system would be a great low cost alternative to a Noveske Afghan. Just sayin'...)

A carbine length gas system is harder on bolts. This is becasue the gas impulse impinging on the bolt is stronger due to the shorter length of travel the gas has in a shorter carbine-length gas tube. The increased strength of the gas impulse decreases the dwell time of the bolt, meaning it unlocks and starts it's reward travel before the case cools and contracts. This makes extraction harder and increases the shear force on the bolt lugs.

That said, a heavier carbine buffer - H, H1, H2 types - mitigates this and returns the dwell time to nominal levels becuse of the additional mass/weight the BCG has to push against IOT begin the extraction process. Hard extraction was the main reason the mid-length gas system was developed in the first place.

Good luck on your build.


I'm so glad to see you made it on Leb. As soon as I read this this morning I thought of you. :thumbs:

Great to see you on.
Sharkey

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