13.9 pin & weld AR-10, receivers (roam rifles R-10)and handguard (darklite) are magnesium alloy.Faxon big gunner barrel and JP enterprise low mass bcg. 3 mags &. 180 rds of 7.62nato, and 10rds of Hornady match 168gr. The 168s seem to run the best through this set up. Toped off with a monstrum 2.5-10