re: DPMS LR 308

DPMS told me that a 165 to 168 grain amercian made cartridge was the most accurate. DPMS said that I needed to shoot 150-200 rds to get it broke in but I heard that is overkill (no pun intended). I bought three boxes of HMS berger 168 grain BTHP to break it in and probaly won't use all of them. I will probaly hunt with whats left and plink with some cheaper. I have another question regarding optics. I ordered a leopold rifleman 3x9x50 scope with extra high burris rings. I've been told that it is to big and will not work very well. What say you, should I go smaller or stick with what I ordered?