"They all have the same feed, but there's an unofficial version of XAP-04 and XAP-05 using SP-5 9x39mm. These weapons are designated as Short Automatic Weapons, without counting the feed they are totally SMG and there are conversions for 9x39mm cartridge, but these are the official versions. If you want we can perform conversions for you, but i guarantee that, it will be definitely more expensive, and the only changes will be less recoil and not sure about effectiveness, because this rounds we use are what we call universal for assault rifles, so they are quite deadly, that's the point for our 'Short Automatic Weapons'. I don't know if you are following the concept here...and our best achievement is to use the same feeds, you can swap any clip from any other of my automatic weapons. But for example, the XAP-05 can only have normal clips, it can't have C-mags or box, and it wouldn't be very recommended, this is only impossible because there's this rail in from of the trigger to help the clip slide into place. Also because you are supposed to grab the clip, and this rail ensures that the clip doesn't come off while shooting."