FWIW, I'm shooting plain base cast 30:1 alloy thru a can, Alox lubed, 12 twist. Not a gas gun but it works quite well, this at 50 yards.
A friend just used some of the same thru a single shot .300 BO, 8 twist suppressed, zero problems. Another project of his, also suppressed is a 77/44. 50 yards, 3 on the left part of adjusting zero, 3-in-1 on the X is the final result. Plain base Lyman 429244 also 30:1 at about the same velocity, same lube.
.22 cal cast bullets aren't much of a mystery.
They shoot OK.