.06 is a great elk cartridge. I use 165 grain and am pleased with its performance. Not qualified to comment on the 150 grain. As stated above try some different rounds and see what flies out of your rifle best. Get in the best shape you possible can. People spend thousands of dollars on a hunt. Spring a few hundred more on a personal trainer if necessary for the summer and until you hunt. The better shape you are in, the more you will enjoy the hunt, and the more opportunity you will have to fill your tag. If you can, go out a couple of days early and camp out in the area to give your body a chance to acclimatize to the altitude. Its not always necessary, but altitude sickness can make a hunt misserable at best and can be deadly at worst. You will have more energy for the hunt if you give yourself a day or two to acclimatize. You'll still probably find yourself gasping for air after that soup you call air in the midwest!