yes, i have seen 870s in military service. not being a southpaw..... i wouldn't think that the 870s safety would really be that difficult to operate for lefties. not as quick or natural, but not difficult.
as a side thought, why would the military request an ambi safety for a shotgun, when the rifle paltform has no such thing (m4/m16)
as a side thought, why would the military request an ambi safety for a shotgun, when the rifle paltform has no such thing (m4/m16)