My cousin and I talked about 444, but my experience with it in my 410 pistol shows the simi rim is much more prone to slip behind the extractor.7x57R,8x57R, 7x65R,9.3x74R, 30-40 Krag, 303 British can all be used( 30-40 & 303 a little small)but I had more of the 7x57R-there is nothing magic about that particular case.
Mike