AR 9mm ..What weight should I use and why

[ding126]

I'm building an AR 9mm carbine..semi auto What buffer weight would you recommend and why. Here is something from spikes..so it made me wonder which one to buy.

Standard CMT carbine buffer - 2.9 oz.

CMT H buffer - 3.8 oz.

CMT H2 buffer - 4.1 oz.

Armalite H3 buffer - 4.7 oz.

RRA 9mm buffer - 5.5 oz.

ST-X SS 9mm buffer - 6.0 oz.

ST-9X SS Extended 9mm buffer - 8.5 oz.

ST-SST - 7.0 oz.

[AR15barrels]

I would go with the extended 9mm buffer.
They don't break nearly as many bolt catches if you are running colt or CP mags with a bolt hold-open function.

[ding126]

Thanks, I was hoping to get a reply from the expert.

[AR15barrels]

You might also look into the buffer for the 5.7 as I think it's the proper length too.