Wa shan Sig P220 and as all wa shans full metal this one is firing MGC P220 rounds which fit without any mods. This model did not fire that well from new and a good friend had to play around a bit with it as it seemed to havfe feed problems. It now works well but what i have found is the mag lets it down if you put just 6 rounds in it it will work fine any more and you get jams it only takes about 9 in the mag anyway so not a big deal. i dont have an MGC p220 mag to try (i did have one but never tried the damn thing god knows why) so may just have to purchase a mag to see if it fits could well cure the feed problem and allow more than 6 to be loaded.
Not sure why the slide was locking back but now is not will have to check i over when i have time got to be something simple with the slide lock bar or the mag itself. rounds go straight up so you dont have to worry about them flying into nooks and crannies where you will never find then.
https://youtu.be/LcznPMAmWDI