Adams Arms PDW length Piston question

[codyusaf04]

I'm thinking about buying one of AA pistons for my AR pistol upper that i'm gonna put together for 300 Blk. I want to be able to adjust my gas pressure for subsonic to make the rifle run as smooth as possible. My question is...are the adjustment knobs on the piston only changeable for preset positions or is it similar to many of the adjustable DI gas blocks where it's is simply a free moving screw that you can move on your own to very finely tune the gas setting?

Thanks in advance for your input and advice!

---Molon Labe---

[justin_247]

I'm thinking about buying one of AA pistons for my AR pistol upper that i'm gonna put together for 300 Blk. I want to be able to adjust my gas pressure for subsonic to make the rifle run as smooth as possible. My question is...are the adjustment knobs on the piston only changeable for preset positions or is it similar to many of the adjustable DI gas blocks where it's is simply a free moving screw that you can move on your own to very finely tune the gas setting?

Thanks in advance for your input and advice!

---Molon Labe---

(a) I suggest you go to 300blktalk.com and speak with them. They have all kinds of info on problems with such systems, and generally the SMEs over there don't see the point.
(b) Lots of people have problems with various 300 BLK setups running subsonic ammo reliably as it is. You're just introducing a new set of problems.
(c) If you're going to buy a 300 BLK piston system, I would buy a complete upper that was designed for it from the get go. AA and PWS both sell such uppers.
(d) 300 BLK was designed for DI systems, so an adjustable gas block is probably a better route to go.

[codyusaf04]

thanks for the input man...I'll checkout that site! Never realized a forum was setup for.300blk.

[UrHero]

From what I understand the AA XLP is the only setup they have that will run reliably with .300 blk, and only with the voodoo barrels. I imagine they did a lot of work tuning the gas port to work with the short stroke piston.

I agree that you're probably better off just buying a complete upper.

To answer you other question, the AA gas blocks all have preset positions. You can't tune them the same way you would an adjustable gb on a DI system. The XLP is a 7 setting if I'm remembering correctly, as opposed to the 3 setting on their other kits. I'm sure that lends to getting it to work on the .300 as well.

[codyusaf04]

Thanks! I think that's the route i'm gonna go with a completed upper