From Ammo To Go:

Technically, both the M193 and M855 are military cartridges. Like most military surplus supplies, there are strict rules around civilian ownership of M193 and M855 ammunition. However, the average Joe can get his hands on loads nearly identical to this military ammo, even though that ammo may not be actual “mil-spec.” Some of these loads are even manufactured on the same lines that make ammo for the military at Lake City’s Army Ammunition Plant.