Thompson magazine converted to 22 cal rim fire

[browningautorifle]

First time I've seen this one too, the one I'm familiar with is the long curved mag and the block that fits the mag guides on the receiver. Then you can either remove the whole affair of the small curved .22 mag by itself. I examined them back then but didn't buy one, my mistake. Mind you, I'd need two boys with buckets to keep ammo to it while on the range...

From what I get for info at the time, the drop in bolt and barrel...either worked well or didn't. I bet ammo type had a lot to do with it like many other firearms...