The RCBS 'X' die works as long as you follow directions as far as case prep. I've been feeding my 7.62x51 gas guns from this die for over 15 reloads without any problems. The initial prep was a bit of a pain (about 1k milsurp brass), but smooth sailing since then. You can get some deformation if your expander is binding. Inside case neck lube (mica or graphite) can solve this as well as polishing the expander.
"Of all the things I've lost, I miss my mind the most." A. Brilliant