Maybe try another lube?? My 338 seems to be one of the easier rounds to size in terms of the pressure that it takes to get the sized case out of the die. Also, with semis, often times you may want a small base sizing die. Semi autos won't have the camming power of a bolt action, and many standard length sizing dies leave the base of your brass a little enlarged from the last firing. This could be a disaster in a platform that will fire when not totally in battery, such as an M1. Your AR platorm won't give you that problem.
