i don't believe the .222R is much diff. from the .222 except you may have to keep the pressure down somewhat......I'm having good luck with 20.5 grs. H-322 and the 50 gr. Nosler plastic tip.....best load to date and probably close to max. for the .222R.
My 222's loved the 52gr MK's and I bet the Vmax/Amax would do well too.
I used H322 most of the time but also H335. I bet benchmark would be a winner. Settled on the CCI 450 primer for 223/222 stuff.
A very nice cartridge.
Jerry