I would suggest this sort of thing would need to be undertaken by a specialist ordnance depot at a base workshops. While the equipment could be made fairly mobile, the conditions under which it would need to be operated (clean workshops, non-spark flooring, bunds, etc.) couldn't. It is actually a highly specialised job and one that shouldn't be undertaken lightly except by those qualified to do so. Ammunition handling, storage and maintenance is a specialist role in most Armies and the Ammo Techs have to undergo specialised training for it, particularly with concerns towards safety (and safety can't be drummed in enough, you don't get second chances with ammunition).