I have run RL15 in a m14 before My records show that I had 42 grains behind a 165 gave me good results with not too much secondary pressure on the gas system.
"It did not beat the Operation rod to death'
that's important !
Good luck you have a fun and real rifle to shoot there.
Some shooters here in the U.S. will not shoot the 180 grain bullets, I am one of them also, it's too hard on the M14 action. let me know how you do.