I just logged ~200 miles well off the asphalt surveying wildlife east of Lewistown over 4 days. I saw plenty of mule deer (and elk). Unfortunately the landscape is popcorn dry going into the second spring without rain. Most the animals were near water sources (the Missouri River, natural seeps, or cattle tanks if turned on). The best mule deer I ever shot was in the Missouri Breaks, a .270 Win pushing a Barnes TSX 140 gr. I jumped him out of a deep coolie, and he made the mistake of pausing at the top of the next ridge about 200 yards out. I always carry a set of shooting sticks and popped him about 10 seconds after settling to one knee. It was a high chest shot, must have also shocked his spine too as he instantly collapsed, and was DRT when I got across to him. My advice would be to find a real accurate load at 100 yards, then practice with it to 300 yards. A lot of deer will be observed at far past that distance, but won't be approachable because of terrain. But others will present quick close shots for the same reason. Conditions in that region can also be quite breezy, so I never plan for true long distance shooting. Better to have a gun you are willing to carry far than one designed to shoot far (500+), and the M12 is a good fit. Lot of good advice above by MTDDFAN. But I would also recommend a mono because I don't like lead grit in my meat. I've never tried the Hammers, but you have me interested in buying some! Good luck.
