The more you kill the less you rely on power and the more you rely on placement, I think. Commonly, the folks gunning the most powerful armament don't have many kills under their belt. Of course that is an oversimplification but confidence comes with experience.
And I have come to notice the amount of crap mounted on their rifle is inversely proportional to the amount of experience they have.
A reliance on gadgetry instead of trigger time and experience..
"...the left considers you vermin, and they'll kill you given the chance..." Bristoe
