Chambered in 9MM and feeding from Glock magazines, it comes standard with a 5.5 inch 416R Stainless Steel barrel. The bolt, front trunnion, and steel upper receiver all feature a Nitrided finish for excellent corrosion and wear resistance. The lower receiver is milled out of Billet Aircraft grade aluminum with a Mil Type 3 Hardcoat Anodize. At the heart of the TAC-9 is an all steel bolt which works with a standard AR-15 fire control group. This offers superior reliability and maintains the same manual of arms that users are accustomed to, decreasing training time on the new platform. You can drop in a lot of your favorite aftermarket parts as the Billet Lower Receiver is milled out like a standard AR-15 trigger pocket.