4.5" .22LR Upper Receiver Build Kit | 4.5" Barrel | 4.25" Rail | Flash Can | BCG & CH ***ASSEMBLY IS OPTIONAL***This .22 Rimfire Upper Receiver comes with our precision 4.5 inch barrel and a 4.25 inch Free-Float MLOK rail, with the flash hider extending past the handguard. The bolt is made of all stainless steel construction and we use an anti-jamb dedicated 22 charging handle. Our upper receivers are fully compatible with CMMG or similar 22 components. Our barrels and bolts are fully interchangeable and follow the same pattern as CMMG. Caliber: 22LR Upper Receiver: Slick Side Forged 7075 T6 Bolt: Stainless Steel Construction Barrel: 4.5 inch / 1:16 Handguard: 4.25 inch Free-Float M-LOK Muzzle Device: Flash Can Charging Handle: RTB .22LR Polymer Charging Handle Compatible with standard AR lower receivers Made in USA Please note: All semi-auto rimfire firearms operate best with quality copper plated and full powered or high velocity 22lr ammunition. Although .22lr AR builds do not utilize the functionality of a buffer or buffer spring, we still recommend using both to provide a stopping point/wall that prevents the 22 bolt carrier from moving rearward. Using a buffer and buffer spring will prevent light primer strikes. This is true for all Ciener/Atchisson 22 pattern platforms. All NFA/ATF Rules Apply Depending on your state and local laws, you could use this barrel with a lower receiver that is a Registered SBR, or Pistol. Possession of this barrel along with a Non-NFA lower receiver may be Prohibited. We are not lawyers and the above information is not legal advise. Make sure you understand the most up to date federal, state and local laws before proceeding with this product. SKU: RTB-UBK-22LR45 UPC: