New Frontier Armory PC Upper Gen 2 LRBHO 9mm/45 ACP Billet Upper

New Frontier Pistol Caliber Billet AR-9/45 Slick Side Upper with LRBHO - Gen 2 Features Machined from 7075 T6 aircraft-grade billet aluminum Matte black hard-coat anodized per Mil 8625 Type 3 Class 2 Compatible with all standard AR-15 / AR-9 components and most aftermarket parts Manufactured to MILSPEC on state-of-the-art CNC equipment for consistent quality parts and exacting tolerances Save money by building your own AR-9 rifle or pistol from the ground up, exactly the way you want it configured Designed to match lines with New Frontier Armory C-9 & C-45 Billet Lower Contains integrated Last Round Bolt Hold Open (LRBHO) technology (PATENT PENDING) that reliably holds the bolt open when the magazine is empty LRBHO feature is designed for lowers that accept Glock-style magazines **NOTE -- This upper is not machined for a gas tube as it is intended for blowback gas systems only Specifications Model: PC Upper (Gen 2) with LRBHO -- PATENT PENDING Caliber: Multi (will accept any barrels, bolts, and calibers designed for the PC style platform) Weight: 8.96 oz Measurements: 7.662" x 1.375" x 2.314" Once assembled, the small "hook" end of the wire form in the upper should be pushed up by the follower of an empty Glock magazine, which will engage the bolt catch on the last round fired to hold the bolt in the locked position. If it does not engage, or engages before the last round is fired, you can make VERY SMALL adjustments by SLIGHTLY bending the "hook" end down to lock faster or up to lock slower. They are set and function checked during assembly with brand new Glock magazines and our standard bolt catches. Because of varying magazine specs, changing magazine specs over the life of the product, different pad thicknesses on the bolt catch, and other variables, this adjustment may be necessary for your specific parts. **NOTE: Some rail systems that use anti-rotation tabs may need slight modification to fit this upper. It is designed for flush mounting rails and standard hand guards. The New Frontier Armory PC Upper (Gen 2) with LRBHO is proudly MADE IN THE USA by hard-working American men and women.