Sorry, I should have posted this info. Never meant by any stretch to leave anyone hanging!!! First off, I don't want to say this is how the "Marines" do it...but this is how one former Marine sniper does it. In the field they advocate a boresnake with some G.I. bore solvent. All he ever did was just run the snake thru until the bore looked clean looking thru the action. He did not do anything aggressive, like to remove copper, mainly I think because they just didn't carry the necessary stuff with them into the field. On the range or while on post it was different, they would do all their shooting on the range for the day and then clean the barrels. He said they would use a cleaning rod with solvent and a brush and scrub back and forth like 25 or 30 times. Repeat and then run patches until they came out clean. If I remember right he kept two boresnakes, one for use with solvent and the other soaked with LSA/CLP type oil. This one was used on the last pull to wet the bore for storage, etc. They were given all kinds of bore cleaner and he said they tried it all, but at the end of the day they pretty much stuck with the G.I. bore cleaner.
That was for the M40's...for the M4's they pretty much did the same thing, but he did say that a lot of the guys bought the Leatherman Mutt tool, mainly because it had a device to scrape the carbon out of the bolt carrier and off of the bolt. He said that when deployed maintenance varied from one soldier to the other on the M4. Some were fanatics about keeping them clean and others not so much. They were almost always told of weapons inspections with enough time to get the weapons clean and made things right when they had to, otherwise they shot the barrels right off the rifles and didn't care.
He told this story of his first deployment to Iraq...he wasn't a sniper yet, just in a mobile assault platoon. They flew in low to their FOB and a few clicks out there was this little town or village. From the air in a CH-53 it looked like the entire town was all children except for a few adults. They surmised that it must have been a place set up for a bunch of war orphans. A few months later they finally made a patrol thru this place and they got the real story. It seemed that Saddam Hussein didn't want the rest of the world to know they had any "defective" citizens in Iraq, so he rounded up all the dwarfs and sent them there to live in hiding. Absolutely no news media people were ever allowed near the place. It was run by one of his brother-in-laws or cousins who was given this job {being the sheik of a town full of dwarfs} as punishment for some prior insult or improper comment. The "sheik" refused to leave and just continued doing his job because at that time Hussein had gone into hiding but was still alive. Many Iraqi's were very afraid of him and believed he would somehow manage to come back and get back into power.
The sheik was one of the nicest people he met there and invited several squads to his house for lunch.
Not much to tell on the cleaning thing, but again, sorry to leave anyone hanging. One thing to remember, it wasn't benchrest shooting...on a man size target a hit is a hit and an enemy soldier with a 308 hole in his upper torso is out of the fight if not dead. If the accuracy opened up due to copper fouling in the field from say 1" groups to 4" groups, as is typical, that didn't necessarily mean an automatic miss. The other thing was that when accuracy fell of and a good cleaning didn't restore it they were simply issued another rifle.