I agree, most people use the 170 for deer. It packs more of a punch. The 150's are still good and, IMHO, are a little more accurate. I have run both through my Marlin 30AS and both shoot well. If you go way far beyond 150 yards, the 170's will have more pronounced "bullet drop" then 150's, but then again, you never know.... It all depends on what flavor of 30-30 ammo you're rifle likes.

Butch A.