I won't shoot steel rounds, only brass. Last shot this late last year with no problems. Have 2-30 rnd. Mag's. they look to be as old as the gun.
Found this online. Think it relates to this gun, although there is no A after the 3 digit serial number.
SECTION IV: National Firearms Act Weapons
Classified As Curios or Relics Under 18 U.S.C. Chapter
The Bureau has determined that the following National Firearms Act weapons are curios
or relics as defined in 27 CFR 178.11 because of their dates of manufacture. These
National Firearms Act weapons, classified as curios or relics, are still subject to all the
controls under the National Firearms Act. However, licensed collectors may acquire,
hold, or dispose of them as curios or relics subject to the provisions of 18 U.S.C. Chapter
44 and 27 CFR Part 178. They are still "firearms" as defined in the National Firearms Act
and 18 U.S.C. Chapter 44.
• Thompson submachinegun, Model M1, .45 cal., mfd. by Auto Ordnance
Corporation, West Hurley, New York, between 1985 and 1986, having S/Ns from
M100A to M717A.