Best AR gas system for different barrel lengths?

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AJMD429
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Best AR gas system for different barrel lengths?

Post by AJMD429 »

My son is evidently thinking of “SBR-ing” his AR, and asked me my opinion on the different gas lengths for 14.5”, 16”, 18” and whether best gas system length (‘carbine’, ‘intermediate’, or ‘rifle’) would vary with addition of a suppressor.

I have uppers in 16” & 18”, with ‘carbine’ gas and 20” & 24” with ‘rifle’ gas, and that’s it, and they all ‘run’ fine but I have adjustable gas blocks on all of ‘em that I fiddled with until they have just enough to run without the suppressor, and run ‘over-gassed’ if I add the can.

So I know what I have works, but really didn’t know the answer to his question.
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3leggedturtle
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Re: Best AR gas system for different barrel lengths?

Post by 3leggedturtle »

For my thoughts and simple mind i would do a pistol length gas port and use an adjustable gas block. Before the mbsv, was gonna make pistol in 300 or 350 and figured that was the best result.
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horsesoldier03
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Re: Best AR gas system for different barrel lengths?

Post by horsesoldier03 »

With all the caliber variants and special purpose ammo, the AR has evolved far beyond its original form. Does he have any idea which caliber he plans to build? For a SBR it is pretty much a Pistol or Carbine Gas system. If going with the SBR, especially if suppression was going to be in the mix, I would definitely go with an adjustable gas block.
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AJMD429
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Re: Best AR gas system for different barrel lengths?

Post by AJMD429 »

223 I’m pretty sure.

(...cuz I told him he should do the SNR in 300 Blk and have a separate 223 upper in a not-as-deafening length until he actually gets a suppressor, and he CAN’T follow all my advice; it’s against the dad-kid rules... :D )
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Grizz
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Re: Best AR gas system for different barrel lengths?

Post by Grizz »

my question about adjustable gas blocks is whether they will fit inside the closely fitted hand guards that are on my pistol uppers ? the gas blocks i have are tiny.
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horsesoldier03
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Re: Best AR gas system for different barrel lengths?

Post by horsesoldier03 »

ODIN WORKS has some pretty good adjustable blocks that should still fit under a thinner MLOC handguard. Personally if I were going SBR, I think I would try the .350 Legend. I agree on the 5.56 being too loud on the ears with a SBR without a Silencer. My personal opinion is there isn't enough gain to justify paying an extra $200-300 in Tax stamps just so you can cut 4" off a barrel. Especially if you have to spend another $200-300 on a tax stamp to make it where it doesn't bust your ear drums.
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Grizz
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Re: Best AR gas system for different barrel lengths?

Post by Grizz »

thanks. i'll look at them
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Scott Tschirhart
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Re: Best AR gas system for different barrel lengths?

Post by Scott Tschirhart »

On my SBR I do not have adjustable gas blocks for either the 5.56 upper (10 inches) or the .300 Blackout upper (7.5 inches). Both run like a sewing machine, suppressor or no suppressor. The 5.56 has a carbine length gas tube and the Blackout has a pistol length gas tube.
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