Thompson Magwell Mandrel/Repair

[H2munitions]

Another war time kit build. The lower was on the max end of specs. I've seen it with a lot of the thompson upper/lowers fitting tightly or loose once assembled. 

I refit this lower to the receiver so that solved the issue but you can see whoever was issued the gun fought it and beat up the lower with a metal hammer/tool to disassemble. This bent the magwell rail to the point magazines wouldn't slide into the frame.

Measuring a few NOS condition frames show the magwell slot is .195-.200 tall. This one was visibly bent inward and measured ~.182 

Our fix was to machine a mandrel, heat the magwell rails with torch and drive mandrel into magwell. The fix was a success and I thought other thompson enthusiasts would find this helpful/interesting!

[Jim in Texas]

Thanks for sharing.  Please tell me more.  Did you have to harden the mandrel or was mild/annealed steel sufficient?  Did you heat the magwell rails to a specific temperature or color before driving in the mandrel?