About 3 years ago I purchased a 1937A1.  It came with one 50rd drum magazine (blocked to 10rds) and one 30rd stick magazine.  Recently I purchased some surplus GI 30rd stick mags and found that they would not lock up in the gun.  After looking closely at the mag supplied with the gun I noticed that the hole in the back of the mag was elongated, the mags I received had a perfectly round hole.  I took my dremel tool and elongated the hole to look like the one that came with the gun.  It locked in place perfectly.  My question is: Isn't the Thompson made by Auto-Ordnance just like the ones that were made for WWII?  If so, why won't the WWII surplus mags I got fit properly without modification?  

as you can see it's not the same.  semi-autos need to have the hole on the mag ovaled out.  I guess you could probably modify the mag catch instead...

Much better to get another mag catch and mod it instead of Dremeling orig USGI mags
cpermd

i have a thompson copy made by manchester
arms. i have to modify the mags the same way.
thompson mags are still pretty cheap, so go ahead and modify the mags. don't screw with
the gun.

The reason the mags need to be modified is that the demensions of the 1927-A1 were changed slightly, to prevent the gun from accepting full-auto parts.

Auto Ordnance announced that they had spent $100,000 building a gun that "Couldn't be converted to full-auto".  Prior to the 1927-A1 the BATF didn't want any firearm to even LOOK like a Thompson.  Auto Ordnance convinced them, and designed the new semi-auto.  
Within a few weeks of the start of sale, there were adds in Shotgun News advertising plans to convert it to.......FULL-AUTO.

New WWII mags are plentiful and cheap, buy a bunch and modify them.

The upper receiver on the new Thompson is not as tall as the old one.  There isn't enough clearance to use the old GI fixed firing pin bolts.

To answer your question... NO!!!!!!

These "West Hurley" Thompsons have nothing to do with the Thompsons contracted through Auto-Ordnance many years ago. And the mag problem is not just with the "West Hurley" model 27. It also exist with the full autos (model 1928s) from "West Hurley".

But you are correct that the hole in the back of mag needs to be elongated to function correctly.