 The staff of Savage Arms looked for ways to simplify the M1928A1, producing a prototype in February 1942 which was tested at Aberdeen Proving Ground in March 1942; Army Ordnance approved adoption as the M1 in April 1942.M1s were made by Savage Arms and by Auto-Ordnance.M1s were issued with the 30-round box magazine and would accept the earlier 20-round box, but would not accept the drum magazine.