Here's a list of U.S. commercial M14 type rifle manufacturers and their model numbers as best as I have been able to gather. If someone other than the manufacturer made the receiver they are identified as well. For example, Armscorp makes receivers for Fulton Armory. The hyphens in the model numbers are as they appear on the actual receivers. From
m14.freeservers.comA. R. Sales Co. Mark IV
Armscorp (Smith Enterprise and Armscorp made receivers) M14 NM, M21
Entreprise Arms (ABNI made receivers) M14A2
Federal Ordnance M14, M14A, M14SA, CM14SA
Fulton Armory (Armscorp made receivers) M14
Hesse
LRB Arms M14SA
Mauntz / H&R Gun Co. Semi Auto
Maunz Mfg. (Smith Enterprise made receivers) U. S. RIFLE
Sarco (ABNI made receivers) M21
Smith Enterprise M-14, M-14 NM
Smith, Limited M-14
Springfield Armory, Inc. M1A