Originally Posted By wrc777:
"not for duty use" means it either failed one of the milspec quality standards or was not tested. It could be missing sealant around the primer or bullet, It could be slightly underloaded and not make minimum velocity for 5.56 or maybe even cosmetic reason. However it does pass all commercial specs so it is safe to shoot.
the same reason ALL xm855 is "NOT FOR DUTY USE" .