Cleaning centerfires

With two exceptions, centerfires clean the same as rimfires. The exceptions are 1. gas-powered semi-autos and 2. copper fouling in the bore.

Semi-auto rimfires are blowback operated. The weight of the bolt, the strength of the recoil spring and the hammer spring are calibrated to hold the bolt closed until the pressure has dropped to safe levels, after which the recoil of the cartridge pushes it back to eject the empty and pick up the next round from the magazine. Some centerfire auto carbines and sub-machine guns are delayed blowback; they use some type of mechanical lock to hold the bolt closed until pressure drops to a safe level. Gas-powered autos bleed off some of the expanding propellant gas from the bore and use it to either travel back through a gas tube and push the bolt back(AR-15/M16), or it feeds into a short gas tube where it pushes back a piston and that is what moves the bolt back. What this all means is that most centerfire auto rifles and carbines have a gas system that needs cleaning. Most of these are fairly simple to take down and clean out; some type of bore cleaner or carbon cleaner to get the fouling off the parts, a bore brush the right diameter to clean the tube, a little lube, and you're done. I'm not going to get more specific than that, there are enough variations that you need to check the specifics for your gun for details.

The bore is where things get fun. The higher pressures and velocities of centerfire guns, especially rifles, tend to cause traces of bullet jacket to rub off on the barrel walls, and if you're pushing cast lead bullets without gas check bases too fast, you can foul up a barrel both badly and fast. If a bore is nice and smooth jacket fouling(usually a copper alloy) may not be much of a problem, though with some of the very high-velocity cartridges it can. If the bore is rough, or has some mild pitting, it can foul rapidly. In either case, sooner or later, you will have to clean this stuff out. There are some really good copper solvents out there now, Sweet's 7.62 for instance. And Brownells has a new stuff called Copper Melt that's supposed to work very well. All of them require a brush and/or jag and patches. Generally, push a wet patch through to clear powder fouling, then a wet one or two- or a brush- to work the cleaner through, then let it sit a few minutes, then a couple of dry patches; if you see blue, it means copper coming out so you repeat until no blue, then dry out and oil. READ THE DIRECTIONS FOR THE STUFF YOU ARE USING, this is only a general procedure I've listed. Some people will plug the breech end and pour the barrel full, letting it soak for long periods, but some of the solvents specifically say not to do that with them, as in some cases it may cause damage to the barrel. So read the directions.

A badly fouled barrel may take a lot of scrubbing and soaking and a pile of patches to get it all out. Here's another place where I'll recommend the FoulOut. It takes a while to get heavy copper fouling out, but you don't have to scrub back & forth, and no worry about possibly damaging the bore. But READ THE DIRECTIONS, because if you don't use it correctly, especially in the first hour, it CAN cause pitting.

There's one other thing you run into with centerfires, especially if you shoot old or military surplus ammo, and that is corrosive primers. They're not actually corrosive, but one or more of the chemicals used in them, when they burn, produce traces of chemical salts that are deposited in the bore(and gas system of autos, and maybe on the bolt and in the action). Salts attract moisture, and moisture causes rust, so... Most standard gun cleaners will not get rid of this stuff, as they're petroleum or synthetic-based, and the salts are water-soluble. So there are two ways to get it out; soap and water, or one of the cleaners designed for corrosive primer residue. I've got a bottle of the old U.S. Army bore cleaner intended to clean this stuff; it's smelly, but it works. A place called Empire Arms, in their FAQ section, recommends mixing sudsy ammonia, the standard household stuff 2- or 3-to-one with water, and that works. These all contain something that will dissolve and flush away the salts. Best results seem to be to hit the barrel with a damp patch or two while it's still warm from shooting, dry patches to clean it out and a little oil. With autos you'll have to get the gas system too. One thing I've used on bolt rifles is Sweets 7.62 solvent. It reeks of ammonia(it's also a good copper cleaner) and seems to do the job nicely. I also tried it on an SKS after shooting suspect ammo, using a patch damp with it to swab out the gas tube and wipe off the piston; no rust seen. Really, cleaning after corrosive primed ammo isn't that bad, just take care to do it soon after firing; you can't leave it for a few days like with non-corrosive ammo, ESPECIALLY if damp weather or if you're in a humid climate.

I should note that the stuff that cleans corrosive priming residue also does a nice job of cleaning black powder fouling.

One other thing I'll mention is run into with shotguns, and that's plastic fouling in the bore from shot cups and wads, and in some cases from plastic buffering material. There are solvents made specifically for getting that stuff out, but I haven't had any experience with them; so far a brass brush and regular solvent has done the job. If you've got a bad case of this stuff, one thing you can do is put a brush on a rod and chuck the other end into a variable-speed drill, dip the brush in solvent, and run it back & forth as the drill rotates it. There's one other thing to try in a really bad case...

My dad was helping another trooper clean his shotgun up before an inspection, and it hadn't been cleaned since he'd last qualified: the bore was the nastiest thing I'd seen in a while. Dad finally took a 1/2" dowel and cut a slot about 6" long in one end, pulled a Scotchbrite pad into the slot, soaked it in solvent, chucked the other end into a drill and went at it. We had to flip the pad over to get fresh surfaces about halfway through but it finally got it all out.

That about covers it. I'll repeat, this isn't the 'be-all and end-all' of cleaning instructions, but it should cover most things. I'll also repeat, if you're not sure of the procedure to use on a firearm, CHECK THE DIRECTIONS. Or FIND SOME! So take the time to do it right, and your piece should keep putting lead downrange for many years to come.