The Geissele Super Duty Complete AR-15 Upper Receiver comes with more options than a 1970s Cadillac, including Geissele Sparkout Muzzle Device, Geissele's Super Modular Rail M-LOK® handguard, and their ambidextrous Airborne charging handle. A tooth in the top rear of the SMR handguard mates with a notch in the upper receiver to prevent unwanted handguard rotation that could compromise optic and/or backup sight alignment. Inside, the Super Duty Upper Receiver has Geissele's Reliability Enhanced Bolt Carrier Group (REBCG). The carrier is machined from extra-hard 8620 carbon steel with extended upper rails to ensure ultra-reliable feeding. (The chrome-lined gas key is, of course, "properly" staked.) The bolt itself is forged from Carpenter 158+ steel alloy, which is far stronger than standard Carpenter 158 for a service life up to 5 times longer than a plain mil-spec bolt. The strongest bolt and carrier in the world do no good if they're compromised by a failed cam pin, so the cam pin is machined from a medical-grade steel alloy called H13. The entire BCG is finished with Geissele's tough, chrome-nitride "Nanoweapon" finish that has a surface hardness similar to synthetic diamonds. Self-lubricating Nanoweapon is highly resistant to fouling and so is very easy to clean.

• Complete AR-15 upper
• Ready to install on a mil-spec lower
• Chambered in 5.56 NATO (.223 Remington compatible)
• Mid-length gas system
• Pinned-on low-profile gas block
• Super Modular Rail M-LOK handguard
• Reliability Enhanced Bolt Carrier Group (REBCG)
• Ambidextrous Airborne charging handle

Each Super Duty Complete Upper Receiver is fitted with a cold hammer-forged 14.5" carbine barrel manufactured by Geissele in their own factory in North Wales, Pennsylvania (not outsourced!). Chambered in 5.56 NATO, it has a chrome-lined bore and a phosphate exterior finish. The mid-length gas tube reduces the velocity of the gas for less violent, more reliable operation of the bolt/carrier group. The Geissele Super Gas Block is pinned to the barrel, so it's not going to move - no matter how many rounds you cycle through this bad boy!