I've burned a lot of RL 15 in some 308s. but never with a 150 gr bullet. But I think you should be able to work up a good load in a short time using your RL 15.
My 1:8 twist 22-250 likes IMR 4831 and a 75 gr AMAX. My 1:8 twist .223 Tikka also likes them. Hornaday stopped making the 75 gr AMAX but but I bought enough to last me a long time.
After reading this I decided to add my 30-06 the hunting line up this year. Can't remember last time I shot something with one. My old load was a 165 gr bullet with IMR 4350. This time around I decided to use a 165 AB with Reloader 15. Ruger No 1 with a 22 inch barrel getting 2900 fps. 5 shot...