If you don't clean your rifle, which includes the chamber every time, I SAY AGAIN, every time you use it, you deserve to have buildup.
This religious need to avoid cleaning weapons is insane. I have seen men die because their weapon wasn't clean. It wasn't just once and it wasn't just the M16 either.
I will give you an iron clad guarantee. Don't clean your weapon and sooner or later it will fail you. That is an absolute.
I love the pistol folks. They believe that if their chosen pistol jams in less than 1000 rounds, it is sensitive.
I have been in a bunch of fire fights. Even with a rifle I don't think I ever went past about 250 rounds. Not a battle, a single firefight. In a pistol, if you unload more than 3 to 5 magazines in a fight, you need more than a Pistol. After every fire fight I was in, after taking care of business (which included reloading our used up magazines with what ammunition we had in bandoleers we were carrying, or were resupplied with.) We cleaned our weapons, then we ate, or what ever.
Often we dug in, and before going to sleep or eating we cleaned our weapons. For civilians the excuses I hear the most are. I am testing my weapon to see how dirty it can get, BS! or I was so tired I had to go to sleep. Clean the weapon then sleep, not after.
CLEAN THE WEAPON.
I have heard all the criticisms about "OVER CLEANING". No such thing. If you are cleaning your weapon appropriately it will not be damaged, but it will be clean.
I don't know of any fighting professional in any agency/organization in the world, that heads into a potential action with a dirty weapon. Only a fool would.
CLEAN THAT WEAPON, EVERY TIME YOU USE IT. No exception, no excuses.
You don't eat or sleep until your weapon is clean.
Besides combat experience, I am a Former D.I. I don't consider the cleaning of fighting weapons a small thing. Today, weapons like my XCR, SIG's, Glocks, HK's etc... even my 1911's accept more dirt/fouling than they used to. Doesn't change a thing.
Clean them properly after each use. Don't forget to clean them if you haven't used them for awhile either.
By the way, I was asked to leave the Drill field for suggesting rather strenuously to a young recruit that his rifle wasn't quite clean enough. That recruit kept his rifle clean after that Come to Jesus conversation and conversion.
Go figure.
Fred