Since when was the M27 the best camping gun? LSAT all the way.
If you want the best camping setup, I have it for you right here. This is the setup I've used since the 2nd week of this game and still running strong.
LSAT w/ Thermal and silencer
No sidearm or tactical
IED (duh)
Amplify, Scavenger, Blast Shield, Blind Eye, Double Lethal
Best killstreak setups:
IMS, Gryphon, Loki
IMS, Sentry/Trinity, Vulture/Battle Hind (cover your back or get free kills)
IMS, Sentry, Helo Pilot