AR10 Buffer/Tube/spring compatibility

T22 · Nov 6, 2020

So I bought a S&W M&P10 earlier this year. It came with a PRS stock, a Kyn-shot Hydraulic rifle length buffer, and I'm presuming a standard rifle length spring. It was a nice setup but it was WAY too long and heavy. I swapped out the whole back-end for a carbine length tube, carbine spring, and carbine length buffer. Was about to head out to the range to try it out yesterday and discovered that the bolt stops about 3/4 of an inch in front of the bolt catch.

My question: what are my options to make this all work out. Do I need a short (2.5") 308 buffer? Or an A5 or PA10 buffer tube? Both? If I go that route will I actually need to buy the A5 buffer/spring like they recommend or could I make the setup work without it? Is there another option I haven't even thought of?

Beekeeping1341 · Nov 26, 2020

I would just get an ar 10 buffer kit if I were you. Aero makes one that I have used and its been 100% reliable.

powermad · Nov 26, 2020

My AR10 uses the longer extension, .308 spring and carbine standard buffer.
The extension is the same length as the Vltor A5, but you can't use an A5 buffer with a .308.

I swapped that out for a LuthAR stock and A2 tube.
It's kinda heavy and I had to turn up the gas to cycle properly.
So I put it back the way it was and used a Vltor Emod stock instead of the Magpul one it had.

The A5 system is for AR15's.
7/8" longer extension, A5 buffer and a Rifle spring.
I have that system with an A5H2 buffer in mine.

On my AR9 I use an AR15 carbine extension, Rifle spring and A5H4 buffer.