If you're looking to build something different than another 5.56 AR-15, then why not a pistol-caliber carbine designed to take Glock pistol magazines?
These FM-9 Billet Lower Receivers are totally stripped and ready for all standard mil-spec AR-15 components, making them a solid starting point for your novel PCC build.
Compatible with all 9mm Glock-style magazines and featuring last-round bolt hold-open, these stripped lowers are machined from 7075-T6 billet aluminum and feature an all-black finish. The receivers are completely made in the USA and are covered under a lifetime warranty.
Big Book Catalog, Issue:72, Page:009