High primers are usually the problem.
I reload for the M1 Garand, and have been for several years. Many thousands or rounds reloaded and fired using regular CCI 200 LR primers.
You need to use proper and correct reloading procedures.
"The Marines I have seen around the world have, the cleanest bodies, the filthiest minds, the highest morale, and the lowest morals of any group of animals I have ever seen. Thank God for the United States Marine Corps. Eleanor Roosevelt, 1945"