watched the demo.. have to say that 1 min watching me playing isn't quite enough to suspect me as a cheater.
Anyway i do lots of prefire/wallbang on DM coz of the many campers there are, with much experience u also check ur radar to know where ur mate died. And after quite some time u know where they will camp and u can hit them by firing through wall. If u hit him ur lucky if not doesn't matter , its still a DM.