A friend on another forum was just tinkering and came up with this. I find myself quite intrigued. Biggest challenge would be finding appropriate jacketed bullets heavier than 210 grains, or figuring out how to run cast through the AR gas system.

https://levergunscommunity.org/viewtopic.php?t=92362

Cast projectiles of plain base or gas checked variety shoot well thru AR-15 direct impingement or piston gas systems.

The chamberings that I soot cast thru AR platforms-
223,224Val,6.8SPCII,300BO,300HamR,7.62x39,350L,
375SOCOM,450BM,458SOCOM,12.7x42(Beo)