Complete bolt assembly is precision machined from an ultra-strong steel alloy to last up to 10 times longer than a standard carbon steel bolt, minimizing the risk of bolt failure during a critical engagement. SAE 9310 steel has a tough, ductile inner core highly resistant to stress fracturing, with a hard outer surface that resists galling and wear, to ensure a service life of up to 60,000 rounds. This is the same steel used in the transmission gears of Formula 1 race cars, so it's ideal for high-impact, high-heat applications like sustained full-auto fire. Meticulously machined radiuses on all 90-degree corners on the locking lugs help distribute impact force evenly and further red Mfg: J P Enterprises SPECS: SAE 9310 nickel-chromium-molybdenum steel, black nitrate. Fully compatible with any mil-spec bolt carrier. .308 fits JP LRP-07 and DPMS LR-308 rifles only.