As the title says, I am looking to build a 9mm AR pistol with a short barrel (5"-7.5" range). This is a project that I've been wanting to start for a couple of years now, but I want to get some opinions on components so that I can start researching  and ultimately start buying. I have been wanting to build one mainly just to have another fun gun to take to the range, and to have a project to work on this coming winter. I want to start accumulating parts before then.

For complete uppers, which companies are making quality, reliable 9mm uppers with barrels in the 5"-7.5" range? Would it be better just to purchase a complete upper or build my own? I can go either way.

I would like to use Glock 33 round magazines with the lower. I saw that PSA makes a lower that is compatible. What other companies make lowers that are compatible with Glock magazines.

Lastly, what type of a buffer would you need to use with a 9mm AR running a barrel that is very short? I have seen people running both H buffers and really light buffers, and both groups saying that one or the other helped reliability.

TNW makes a complete pistol that takes Glock mags, the Aero Survival Pistol. The best I way I can describe it is it's a composite of an AR and a Sweedish K. http://www.tnwfirearms.com/product-p/aspx-cplt-xxxx-xxxx-xxxx.htm

I'm building a 9mm AR pistol with a 8.5 barrel right now.

I've been building it in pieces, mostly to keep from dropping a lot of money at one time, so I didn't go with an assembled 9mm upper.  You can go either way.

I can't answer the question about the lower, since I went with a Colt-style lower.

Regarding the buffer, after doing a lot of reading on this board and others, I went with a standard carbine spring and a 9mm buffer (mine is from PSA.)  From what many people have said, start that way.  I also made a spacer out of oak for the buffer tube to prevent bolt stop breakage.

Quarter Circle Ten

RRA Colt style upper, RRA magblock, Spikes heavy buffer, Sprinco heavy buffer spring. Buy upper from Adco in 10.5, have bolt ramped too. Done.

Thanks for all of your replies. I appreciate it!

I built my own 9mm SBR. I started with the Quarter Circle 10 Glock lower and MVB industries stock. I built the upper with a 5" barrel and 3 lug mount and a  gen 1 JP bolt. It has a Odin 5" rail and Trijicon RMO. Runs like a top eats everything and is fun to shoot. I also run a Silencerco Octane 45K on it. Super compact. 9mm AR's super awesome and great fun.