There have been a number of single-shot .50 BMG pistols over the years. None of ’em really seem like the sort of thing I’d want to shoot too often.
This is base don the same Serbu configuration that went kerblooey on Kentucky Ballistics some months back. Except in this case if it did that, it would shoot that endcap right directly into your face. So, ummm, watch out what you load this with.