It wont happen on your Garand. As I said, I've fired thousands of cast bullets out of my Garand (as well as my other gas guns) and never a problem.
I can't tell you about AK's. Don't have one and never fired cast bullets from one.
Keep the velocity to about 1200 fps. That's also the velocity that keeps managers of indoor ranges happy.
Reduced (cast bullet) loads are a means of some good, cheap, practice ammo and can be pretty dern accurate if you pay attention to your casting and loading.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071