Description Threads: 1/2-28, 0.400″ long (rimfire length). We cut a proper thread relief at the base of the threads for compatibility with any 1/2-28 device. Assembly OAL notes: Rimfire barrels sit at a different position in the upper than centerfire barrels due to the design of the bolt. The chamber entrance is about 1.5″ farther back in the upper once assembled. This will result in a shorter overall length of rifle/pistol than the same rifle/pistol built with a centerfire barrel of the same length. 1.625″ of barrel length is inside the upper for rimfire barrels, 0.375″ of barrel length is inside the upper for a centerfire barrel. 7″ rimfire builds to an OAL similar to a 5.5″ centerfire (5.375″ of the barrel is in front of the upper threads) 12.1″ rimfire (Available in Apogee) builds to an OAL similar to a 10.5″ centerfire (10.5″ of the barrel is in front of the upper threads) 16.1″ rimfire builds to an OAL similar to a 14.5″ centerfire (14.5″ of the barrel is in front of the upper threads) 21″ rimfire (Available in Apogee match) builds to an OAL similar to a 20″ centerfire (19.375″ of the barrel is in front of the upper threads)
