Regarding my mentioning the tuning of sniper rifles, let me try to explain:
A sniper has to choose his upgrades, sort out little issues with them, shoot it enough to see if a benefit or not, learn the 'new' personality of the gun after the new parts settle in. I know lots of guys "tweak" their AEGs with upgrades and such, but they don't have to largely deal with one shot 250ft away and possibly lose that target after they shoot, there are always quick follow up shots, something a sniper really doesn't have the luxury of enjoying. So one has to largely tune and LEARN for best effect, where AEG users largely will just tweak. I've waited upwards of a few mins between shots focusing on the right moment to loose my round, and I don't have the luxury of having two or three BBs in the air at the same time.