Re: Looking for an upper for my AR pistol
It would be way easier to buy the barrel at the proper length. Especially if it's a 300 blackout. For 300 BLK the gas port diameter is pretty essential.
If it was me, I'd get a Noveske barrel. They're high quality, and come with a gasblock and tube. If you're not wanting to do super sonic loads, then the 8.2" would be better since it will make for a shorter overall package. On the other hand if you ever think about using this on a rifle, then 10.5" would be better since you could have the local company DBMG install one of their sleeves that make the bbl a full 16" and run a suppressor inside the sleeve.
Personally I own a 300/221 fireball bbl from Noveske. (Works with blackout ammo.) It's 16" barrel. For me I load all my own ammo and it's more of a fun gun. But still, since the ammo is so expensive (Purely in bullet cost and in reloading time). I tend to shoot it less and pretty much always prone out with it. For that, the whole AR pistol thing would kinda suck.
I also built a pistol upper that has a super short 5.56 barrel. I can't remember the exact length but I think it's close to 7.5". It's fun and cheap-ish to shoot. I think something along these lines would be a better alternative.
Now if it comes to wanting to do supersonic loads, the blackout is pretty much on par with 7.62x39. 7.62x39 ammo is dirt cheap and an AK pistol can be had for not much. I have a draco-c that actually shoots surprisingly well. I just couldn't see shooting expensive supersonic 300 blackout ammo in a package that doesn't have a stock when a much cheaper alternative exists.
If SBR's were allowed in our state, I'd probably sing a different tune. As they are, AR pistols (and AK pistols) are just fun toys and not much more.