I'm new to Thompsons and just picked up a new AO 1927. I noticed the fit between the frame and the upper receiver is pretty loose and wanted to find out if this is normal. When holding it, I can feel the frame and the receiver clunking into each other if you just move it slightly. If I shake it or move it left to right you can see the gap between the frame and receiver get larger and smaller.

Below are pics of the frame to receiver gap. Is this normal?