Sure, the 5.56 NATO cartridge tends to run better in longer barrels, but there's still plenty of energy from a round fired out of an ultra-compact barrel, and let's be real: there's some serious allure to an ultra-compact AR-style pistol, isn't there? The team at Stag Arms gets it, so they came out with the ideal upper receiver for your AR-style pistol or NFA-regulated short-barreled rifle. This Stag Arms Stag-15 Tactical upper receiver is outfitted with an ultra-compact 7.5-inch barrel that's equipped with a short, pistol-length gas system that's designed to give you the reliability you need from a short platform like this. The barrel and gas system are surrounded by an M-LOK SL handguard that runs just short of the muzzle, and the slim, open-ended design promotes air flow so your barrel stays cool through rapid strings of fire. The barrel itself is rifled with a 1:7-inch twist rate to stabilize those heavier-weight rounds, so you can get the most capability possible out of this snub-nose system. All you need to do to complete this Stag Arms Stag-15 Tactical Upper Receiver is add a bolt-carrier group and charging handle of your choice, and you're ready to rock.