If your bullets are keyholing at 50 yards, you have some strange sort of problem. From my '06, I get equally tight groups with 150-grain boat-tails or flat-bases.
I do my first sight-in at 25-yards, and then go to the 100-yard target. I've never had any key-holing, ever.
Do you know the rate of twist in your barrel? I'll do some guessing--correct me if I'm wrong: Isn't the BT bullet longer than the RN? So you might need a faster twist to stabilize the BT? Ever load 110-grain, and get nice, tight groups?