? about first 300 BO pistol build

John from MD · Aug 18, 2020

Not sure this is the right forum but mods feel free to move if it is in the wrong place.

I just bought a ABC 8.5 inch barrel for a 300 BO pistol upper build. While I have built PCC's and AR pistols, the only 300 BO build I made is a 16 inch barrel. Here are my questions.

1. What buffer and spring will I need for this build? I am shooting unsuppressed supersonic.

2. What size handguard will I need? I plan to put a 2 inch flash tube on the barrel.

TIA for the help.

outrider58 · Aug 18, 2020

I would go with a Tubb light AR 15 spring and an H2 buffer. You might consider a KAK configurable buffer if you encounter any cycling problems. Some barrel's gas ports can require widening as a last resort.
I would start out with the Tubb/H2 setup first though.

John from MD · Aug 18, 2020

Ok. I have the H2, I need to order a spring.

alucard0822 · Aug 18, 2020

depends on the barrel, 300 isn't as picky as 5.56, I can run my 9" BA barrelled 300 with a standard carbine spring and 3oz buffer, runs anything suppressed or unsuppressed. Have seen others benefit with an H1 or H2 with supers, especially suppressed, but even then it doesn't have the ejection pattern and "slap" in recoil like a 5.56 with a buffer an oz or two too light. As far as the handguard, that is up to you, 8.5= 7.9" to the threaded shoulder, if you are adding a 2" linear comp or something like it it will stick out .9" from a 9" handguard

John from MD · Aug 18, 2020

alucard0822 said:
depends on the barrel, 300 isn't as picky as 5.56, I can run my 9" BA barrelled 300 with a standard carbine spring and 3oz buffer, runs anything suppressed or unsuppressed. Have seen others benefit with an H1 or H2 with supers, especially suppressed, but even then it doesn't have the ejection pattern and "slap" in recoil like a 5.56 with a buffer an oz or two too light. As far as the handguard, that is up to you, 8.5= 7.9" to the threaded shoulder, if you are adding a 2" linear comp or something like it it will stick out .9" from a 9" handguard

Thanks for your input especially the handguard numbers. Math was never one of my strong points. :lol:

? about first 300 BO pistol build

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