Also, from 1960-1964 the only models produced were the E, F and DL. The F and DL had the barrel boss, so the initial model that could use up left over Chicopee Falls non-barrel boss barrels would have been the 99E until the .284 came along. Maybe theyu cut 24" barrels, or perhaps, they were actually producing 22" barrels in Chicopee for the introduction of the 99E .. maybe both.