If you don''t already have some literature on yout TSMG, you might want to get some. You can only shoot so many rounds, and you gotta stay home from the range some weekends.
The 1942 War Department manual, TM 9-1215, has full detail stripping information on the 1928A1 Thompson. On page 25 there is a good illustration of the relationship of the frame and the parts contained therein. Part A is the rocker. Note that the semi-circular cut out is toward the rear of the frame. On the opposite page, page 24, item b (3), the assembly instructions state,
"If rocker is assembled backward, the gun will fire full automatic but not semiautomatic."
I have fired two TSMGs, some 25 years apart, which wouldn't reliably function in the semi mode. One was a Savage-made 1928A1 and the other was an M1-A1. Each time, I found the rocker was mis-assembled. Now that I write this, I realize I've never purposely set my own TSMG up that way. Maybe on next trip to the range . . .
Hope you enjoy yours as much as I have mine. Best regards.
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