How to get bullet kills with snipers in mw2?

Hey guys. (Please don't report me for cross posting, I have NO answers for the other one!) I know very well how to get bpks with every other weapon, (3rd person, highrise.) but what about snipers? My barret 50 cal has only the extended mags left to unlock and i really want to get the mastery. Only problem is, when I try to use the other method, I can't because it aims down the site ENTIRELY and I cannot see through the wall! Are there any other methods to do this? BESIDES boosting?