The MG51 loader is for the swiss version of the MG42. I have heard (repeat, heard) that with some minor alterations they can be made to load MG42 belts (same basic belt as MG 42, different caliber). The MG57 loader is for stg57 magazines. I might order one to see if it can be adapted to load FAL and M-14 mags, since it is set up for the 7.62x51 round.