I have had good luck with R22 in my R77/270 using 150 BTs, NPs and SBs. Don't overlook R17 either.
No matter what you read or are told, work your way up to max for your gun.
jmho
Tim

"The significant problems we face cannot be solved at the same level of thinking we were at when we created them."
Albert Einstein

At Khe Sanh a sign read "For those who fight for it, life has a flavor the protected never knew".