Thompson vs. M3 Grease Gun mags

[Chuck]

Looking at the rear of the mag (you'd see primers from this view), are Thompson mags wider than Grease Gun mags?

Chuck

 

[James K]

The Thompson mag runs .975", the M3 Mag is .980" at the magazine body, but the top reinforcement is 1.075".

They are not interchangeable, and one can't (feasibly) be made from the other. Also, the feed is different, the Thompson being a true double column mag and the M3 a double column but single feed.

Jim

 

[Chuck]

Thanks!