Was he Supply over in the Pacific? It looks he spent most of his time in Supply and he rose from a private in 1941 to a Sergeant Major in 1945. Which might be the fastest I've ever seen a Marine reach Sergeant Major.

He is listed with a MOS of 584 at the end of the war.
You can request a free copy of his records, but to be honest the free copy usually sucks. They do a horrible job usually. They miss pages, or you can't read them. It is exactly what you would expect of a govt employee and being free. I pay a private researcher to pull them, which she usually charges $40 to $50, but you will get them copied right and she doesn't make mistakes. Usually the record books are 30 to 50 pages. I can give you her contact info if you would like. Or I can find the link for you to request a free copy if you choose that route too.
I wish I could have interviewed your father. He was on the front lines of the supply system for the 1st Amphibious Corps and it looks like later the 5th Amphibious Corps. He would have had a lot of first hand knowledge on the shipments coming over. And the supply Marines, especially that early in the War are extremely rare.
Just a weird question, did he ever mention anything on sniper rifles?