From Troy's "Best 5.56 rounds, Cliff Notes":
7. M193-class ammo, 55gr FMJ-BT bullet. True M193 ammo will be sealed at the bullet and primer, will have a crimped primer and bullet, and is a 5.56 pressure loading. 1:12 or faster twist required.
- Lake City M193 (genuine surplus M193; no longer available)
- Federal XM193 (seconds) or XM193PD (thirds)
- Winchester Q3131 (seconds)
- Winchester Q3131A (manufactured by IMI)
- IMI M193
- PMC, '98 and earlier
- South African M1Ax in battlepacks