9mm
6.8mm SPC
7.26x39mm (AK round).
.40SW
.45ACP
.50AE
.50Beowulf
You name it, as long as a magazine will still fit in the lower.
I am about to sell a few old weapons to get a .50 Beowulf
Would love the Grendel, but I’m in Florida and can’t envision a 600 meter shot.