Later M39 barrels are 26" long and are the same pattern as the earlier M39 barrels with the exception of the secondary shank which is eliminated. This final evolution of the Mosin Nagant barrel reverts back to the M91 pattern with three exceptions besides the length. The muzzle end of the shank is turned down to accommodate the rear sight base. The barrel itself has a slightly larger outside diameter and the muzzle is turned down to accommodate the front sight base. Tikka and B barrel M39s are built with shortened M91 barrels that have had the shank and muzzle turned down. This is evident by the smaller diameter at the muzzle which is the same dimension as an M91 barrel at the same distance from the receiver.