I have loaded and shot a lot of RL10x in .223. It is a hot powder and the pressure signs come up fast. If you have the right chamber (NATO) you might get all the way up to 24 grains with a 55 grain bullet but you are going to see some pressure signs. The Alliant load for RL10 is 23 grains in .223. 23.2 is good in my Mini 14 and I go 23.4 in my AR chambers that are Wylde or Nato chambered.
A friend shoots 24 grains with a 50 grain soft point in a bolt action. He says he is not seeing pressure signs. (??) 24 grains in a .222 RM might be worth a try but I would be reluctant to go over this. Of course start lower and work up to it. I did get my best accuracy with RL10 but I suspect my velocities were on the lower side, if velocity is really required for your style of shooting. I have not tried Alliant 15 but if higher velocity is your goal that might be the one to use. It's a real long step between RL10 and Alliant 15.
I think AA2460, AA2495, AA2520, IMR8208 and Benchmark may be better options for 55 and 62 grain bullets in a .222RM but that's just me. I wasn't a fan of CFE223 because the accuracy wasn't very good with 55 grain bullets but it may shine in a .222RM if your barrel is long enough. Have fun.
kwg
Last edited by kwg020; 07/05/20.
