XM193:  5.56mm, 20-round brown box, 500-rounds per case.

XM193BK:  5.56mm, loose bulk, 1000 rounds per case.  Not as pretty as the boxed stuff where some rounds may have small dents, but still goes bang.

XM193A and XM193AF:  5.56mm, rounds packed in ten-round stripper clips, 900 rounds per case.

XM193C:  5.56mm, commercial package, American Eagle Tactical “Black Box”, 20-round box.

XM193CBP:  5.56mm, commercial package, American Eagle Tactical “Black Box”, loose rounds in 200 round bulk (value) pack.

XM193F:  Packaging for XM193 is now done at Federal’s ammunition plant in Anoka, Minnesota, so a new part number, XM193F, was needed for FET purposes.  This is the same ammunition as XM193 and XM193C and apparently replaces both of these items.