Codes for packaging and in some cases maker. For example XM193F is 20 round box packaging, XM193CBP is 400 round bulk packaging, XM193BK is 1000 round bulk package. IIRC LC denotes Lake City brass and AC1 is 420 rounds on stripper clips.
XM855 62gr. Penetrator Ammo. This is the original US Military Lake City Arsenal M855 Penetrator Ammo, steel tipped penetrating core for combat use, with a muzzle velocity of 3,025fps. It is brass cased, boxer primed, non-corrosive and 100% factory new Federal ammo. This ammo comes in 300rd. loose pack cases.
Federal Lake City XM855LC AC1 5.56mm 62gr. FMJ Ball Ammo 420rds on strippers
5.56 Federal Lake City XM855LC AC1 62gr. FMJ Ball Ammo on strippers. This is packaged 420 rounds on stripper clips, packed in a sealed .30 cal. ammo can. It is brass cased, boxer primed, non-corrosive ammo. Each can is marked "not for duty use".