AR-15 300BO, 16" barrel, what gas system?

DaemonAssassin said:

From personal experience with pistol and carbine length gas systems, I'd go pistol length, due to the cartridge being designed around that gas system length. My setup is pistol length gas and will reliably cycle supers or subs.

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BCM has taken great care to ensure the best possible performance and interchangeability. However, due to the large operational range of 300 Blackout ammunition in the market place, BCM cannot guarantee function will all ammunition types in all conditions. These barrels were designed to run with a carbine buffer with subsonic ammo and a H3 buffer with high velocity ammo. Fine tuning may be required in limited instances based on ammo and buffer choices that work best for the desired application. BCM also recommends running the Crane O-ring (provided with all BCM Bolt Carrier Groups) over the extractor with 300 Blackout.

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clandestine said:

Pistol Gas is optimal IMO for a .300, so is adjustable Gas. Messing with buffers is not necessary with a good SLR Adjustable Gas Block.

The BCM/Crane O-Ring can often induce ejection problems from extractor over tensioning and it can cause damage to the casing rim for reloaders.

Use a Colt Gold Extractor Spring and no O-Ring is ever necessary in my experience.

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DaemonAssassin said:

Slightly off topic, but would you recommend a adjustable gas block or a standard gas block for a 12.5 inch, carbine gas 556? Planning to do a pistol build and wanted your thoughts.

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BradMacc82 said:

Originally, the 300BO was optimized for a pistol length gas system - due to the use of subsonic ammunition.

It seems a lot of outfits have finally started getting the gas port diameter correct for reliable operation with carbine length gas - even with subsonic ammo. Which is better, could be debated I guess.

Personally, I've always opted for the pistol-length gas on my 300BO uppers, and adjustable gas-blocks (never know when the desire to suppress will override the bank account). I've never had any issues that weren't induced by the user - or by development loads I was testing.

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12.2" 300BO and 16" 300BO.

Both shot fantastic, both are in new homes.

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clandestine said:

Its a plus in my opinion, but its not a huge improvement unless the gun has a supprssor.

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friendlyhippo said:

You really should do another one, since you know someone with a 30-cal suppressor.

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Mdeng said:

He may know two someone's

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Alphabrew said:

I researched on ARF before building mine and they said pistol length gas

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friendlyhippo said:

You really should do another one, since you know someone with a 30-cal suppressor.

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Mdeng said:

He may know two someone's

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friendlyhippo said:

Looks like i'm trading the mini mill for a MK II TR. might have to chat with you about an appleseed before i venture off to america on a permanent basis.

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