Bergman MP.18 SMG and M1916 steel hand greande

ammunition_belt has been used quite a bit for bandoliers and simple belts with ammunition pouches on them (which is in itself an underused tag that compliments load_bearing_vest etc).

The wiki already explicitly distinguishes between ammo belts and bandoliers, so I guess we might have to rename the tag to something more intuitive at some point if it grows out of hand.