Back in 2017 when PCC was a provisional division in USPSA I put an AR9 together from a mish-mash of different parts.
QC-10 lower with Colt/Uzi pattern mags. At the time the lowers that took Glock mags didn’t offer LRBHO, but QC-10 did with Colt mags. I believe that has since changed and many of the PCC lower manufacturers have figured out LRBHO with Glock mags. If you shoot Glocks it makes sense to use one that accepts Glock mags. Colt mags are ~$30 for a 32 rounder and Taylor Freelance makes a +10 extension for gun games. I’ve never needed more than 42 rnds for a stage.
Upper is a generic AR9 upper w/ the really big brass deflector. Not sure if that was needed or not, but back in 2017 it seemed like the thing to do.
Barrel: Originally I went with a 16” barrel from BA with A2 bird cage. That combo was quiet, too quiet for shot timers to pick up reliably unless the RO was really close. I bought a cheap AR comp with really big baffles and drilled it out for 9mm. That made the shot louder, but due to the 16” barrel my regular pistol ammo was chrono-ing 1,150-1,200 fps (~145 PF). So if I wanted to be closer to 130 PF I had to load some really powder-puff rounds, but that meant I had to keep two loads of 9mm, one for pistol/one for PCC. Doable but a PITA. Eventually I got a Taccom UWL barrel that is 5.5” long with a 16.1” aluminum shroud that is pinned to the barrel. It solved a number of things: it chrono’d low 130’s PF with my regular pistol ammo, it was loud enough for the shot timer on regular setting to pick up even from 10’ away, and it gave me a better balance rather than being muzzle heavy.
BCG and buffer: Originally started out with a CMMG BCG and basic carbine buffer. Experimented with different springs and weights in the buffer. After several thousand rounds I started to get some FTE’s. Ended up replacing replacing them with a BCG from JP along with JP’s Silent Captured Spring system and my ejection problem went away.
The rest of the PCC is basic AR stuff: grip, stock, fore-end… Trigger is a Hypertech bc that is what I have on my other ARs. Red dot is a C-More Railway and a Vortex Razor on a 45 deg mount.
It’s a fun division, I still shoot it periodically but with all the advances in AR-9 technology, specifically with what JP Enterprise is doing with their JP-5, my blow-back operated gun is probably a relic by now.