Geissele Super Duty Mod1 Compelte Upper 10.3in 5.56MM DDC. This 10.3in complete upper chambered in 5.56mm features a nanoweapon-coated HUXWRX Flash Hider-QD muzzle device mounted to an 10.3in Manganese Phosphate coated CHF Chrome Lined 1-7 twist barrel. Our barrels are precision machined and cold hammer forged utilizing the highest quality materials at our state of the art facility in North Wales PA. The carbine length gas tube and Geissele Super Compact Gas Block with bomb-proof installation ensures reliability and optimal performance in extreme conditions. Included is a brand new 9.3in Super Modular Rail MK16 that mates to the upper via a center aligning tab removing any chance of rail rotation. This rail is a variant of the 13.5in SMR MK16 currently fielded by USASOC and renowned by operators for their performance and comfort. Also included is the Geissele Reliability Enhanced Bolt Carrier Group. This Nanoweapon coated BCG features a properly torqued and staked chrome lined gas key. The Cam Pin is machined from advanced medical steel known as H13 which is also coated with Nanoweapon for maximum corrosion and wear resistance. The Geissele Reliability Enhanced Bolt Carrier Group also features extended upper rails providing greater stability and dramatically increasing feeding reliability. The Geissele Reliability Enhanced Bolt Carrier Group comes with the Geissele Stressproof Bolt. Made from Carpenter 158+ directly developed with Carpenter Steel metallurgists to create a material that is cleaner and has less impurities. This makes our Stressproof bolt stronger and more fatigue resistant. The Geissele Stressproof bolt is also forged not machined from barstock. This allows us to optimize the grain structure of the steel to yield a bolt capable of 5 times the life of a mil-spec bolt. Each bolt is rigorously inspected high pressure tested mag particle inspected and Nanoweapon coated. Specifications for Geissele Super Duty Mod1 5.56mm 10.3in Complete Upper: Manufacturer: Geissele Caliber: 5.56mm Overall Length: 19.5 in Barrel Length: 10.3 in Barrel Profile: Tapered Gas System Length: Carbine Length Barrel Twist Rate: 1-7 Threads per Inch: 1/2x28 Muzzle Device: Nanoweapon-coated HUXWRX Flash Hider- QD 556 Finish: Type 3 Hardcoat Anodize Fabric/Material: Aluminum & Steel Steel Handguard Length: 9.3 in Bolt Carrier Group Included: MIL-SPEC Charging Handle Included: MIL-SPEC Magazine Included: No Package Contents: Geissele Super Duty Mod1 10.3in Complete Upper Geissele 08-543S: Super Duty Mod1 Compelte Upper 10.3in 5.56MM DDC