You should be able to get it to work without any shims installed at all. Shims are only used if the bolt barely moves, doesn't release air and then won't reset. If it chuffs and won't reset, then that is bolt stick, not a shim related issue. The shims allow it to release air sooner in its forward movement.
Check for a bad carrier oring. It could cause you to use a carrier that is too tight, which would cause bolt stick.
Except for the Automag in front, its usually the man behind the equipment that counts.