I agree with blumsden. You MUST take the very first clean shot opportunity you have on a mature buck. If you wait on the prefect angle, clear shot, get closer, etc you will wind up going home empty more than not. Big deer don't give you much time. Most of the ones I have killed have not walked out into a food plot or opening and given me time to look at them. I immediately go into "Make this happen no matter what else is going" mode when I see a deer I know I want to kill. It happens very fast. The few mature bucks I have hesitated on to give me something better are still walking around, or on someone else's wall.