Mil spec chrome lined barrels need very little cleaning. The military does not issue copper remover to the troops. If your rifle has a nice long range match barrel treat it like such if not just make sure you get the chamber nice and clean. The piston rings in DI guns require oil every 500 rounds or so. With mil spec guns you can get away with just putting oil in the exhaust ports on the carrier every 500. I regularly run guns well over 5000 without a cleaning by doing this. I use slip 2000 extreme weapons lube. It decrease the carbon build up on the bolt, but any gun oil will work great if you clean every 500 rounds or so. TW25b is great stuff. I love Tetra lube oil and grease. Break free is very good too. There are a lot of cleaning video on you tube.
http://www.youtube.com/watch?v=OXIsKEHo-4g&feature=plcp They all warn not to put anything in the gas tube. The inside of gas tubes do not need cleaning. The gas key on the bolt carrier should be cleaned with those pipe cleaners that come in the kits not the gas tube.