Ladies and gentlemen, I think I have killed my first AR-15 barrel.

About a year ago I shot up the last of the cheap China Sports ammo left over from my Mini-14-is-so-cool pre-AR days through my "beater" de-milled USGI upper and didn't clean it properly.  I think I just brushed it out in the field then stuck it in the corner of my closet.  Now the bejeezus has been rusted out of it, worst I've ever allowed by three orders of magnitude.  I've dealt with corrosive ammo in 8 mm and 7.62 x 39 before, so I should have known better.

I plugged the muzzle with beeswax and filled the whole thing with WD-40.  In about a month I'll take a stainless steel bore brush to it and see if there's anything left, but most likely I'll take this as a lesson learned and an opportunity to set up a National Match upper for the cost of a new barrel and rear sight.

Never believe anything printed on boxes of Chinese ammo.

CK--
 I still have over 2000 rounds of the Norinko 223 in the yellow, redletter boxes, and the white/black boxes. Last year I snapped a few of the caps on a piece of band iron and did not get any rust after letting it sit for many weeks. The headstamp dates were 92 and 93.
 Can you pass along the dates from your dreaded batch?
Thanks,
Randy

The ammo may not have been corrosive.  Letting any barrel sit for a year or so without proper cleaning and occasional reoiling is just asking for trouble.  I also flunked the dumbass test once years ago with a S&W model 39-2.

The ammo I suspect of being corrosive is one or both of two batches:

- Yellow box, red and black lettering, "CHINA NORTH INDUSTRIES CORPORATION", headstamp C J / 92, and/or...

- Red and black box, gold and white lettering "NORINCO/CHINA SPORTS", same headstamp "C J / 92".

I hear what you're saying wjshark and agree that you can't just let barrels sit around uncleaned.  However, I've seen corrosive ammo effects before and this sure looks like it.  If the Norinco is corrosive it's not as bad as some nasty old German 8 mm I used to get many years ago.

The climate where I live is not very humid most of the year so you can get away with neglect better than you could in some places.  My standard practice for firearms I'm not going to use for a while is to clean thoroughly and annoit liberally with rust inhibiting grease.  I also keep silica gel in whatever container they're in.

I've inspected all of my .223 rifles that may have had this ammo fired through it, and they are all OK (because I cleaned them properly).

On edit:  I just got through inspecting (in in a few cases cleaning) every firearm in my house, and that is no easy task!  Even among low-value ones stored in similar conditions to the rusted AR barrel and in similar state of lax cleaning, the AR barrel was the only one with even a trace of brown rust (and it had plenty).  I'm pretty sure that ammo had something to do with it.  It may be only mildly corrosive, but that combined with my negligence it kicked my ass.

I promise to clean my weapons better from now on and never put bad ammo through an AR-15 again.

My Standard Practice is : clean after every shooting session , i never have a rust problem regardless of the ammo i use.

Same here.

I used to shoot lots of the Norinco yellow box .223 with 93 headstamps from a Ruger Mini-14 stainless Ranch rifle. I bet I ran through thousands of rounds of it. Back then, it was the "Wolf" of .223 ammo and since my Mini would digest anything, it was my plinking load of choice. I never had any problems with it, but the Mini did have a stainless barrel.

I did run into a problem a few years ago with the barrels of some of my hunting rifles that never saw a round of corrosive ammo. This includes Winchester Model 70, Remington 700, and a Marlin 30-30. None of them had ever been fed anything other than recent production Winchester, Remington or Federal so I couldn't figure out why my barrels were developing crap in them every few weeks.

Finally, I got a new thermometer for the room where I store my guns and ammo. I mostly wanted to get this to ensure the room temp stayed below 80 degrees in Summer to protect my ammo. This thermometer also happened to measure and display relative humidity and I quickly determined my problem wasn't ammo related. The room was just very humid. So after picking up a good de-humidfier at Wal-Mart and running it a few hours per day in that room, no more problems.

Being you kept your gun stored in a closet (a place where dampness can collect because air doesn't circulate in there very well) that may be as much to blame as the ammo. I suggest getting one of those things and keeping an eye on humidity in the future. It can make a huge difference. Many modern homes are built really well, but some are so highly insulated (as mine is) that they can have trouble breathing. Just a thought.

-Charging Handle

TN redneck cure or kill for a rusted barrel:

Load the rifle
Place rifle in a notch on tree pointing down range
tie a string to the trigger
Step back about 25 yards
Take cover behind a hill or large tree
Pull the string

It will either cure it or kill it.

LMAO! That must be a KY redneck method as well, because I recently watched some guys do this to an old M48 Mauser that was in pretty bad shape. It actually worked and after getting the jagged pieces dislodged, the barrel actually cleaned up pretty well and the rifling wasn't severely damaged. While this sometimes works, I couldn't actually condone such a method as 100% safe. But if the gun is secured, a backstop apparent and you can get far enough away from it, then it may not be too dangerous.

FWIW, I cleaned a rifle barrel out once for a fellow with a steel brush. It seemed to work about equally well as the above method, it just took more time and elbow grease. You may give it a try and see. If a steel brush doesn't help it, ditch the barrel and buy new one. That's about the best advice I can offer.

-Charging Handle

I like the TN Redneck method!

The problem is probably not as bad as I thought at first sight.  I've cleaned out Mauser barrels that looked like all hell and were hard to push a brush through, and had them eventually come out looking OK.  That barrel is a "beater" and if it ends up shootable at all life will be OK.  OTOH it would give me an excuse to build up something nice.

The worst LOOKING barrel I ever saw was on my old Ruger 44 Carbine.  It was black, thick with caked-on junk but it was not rusted in the slightest though there were a few small spots on the exterior.  The powder residue may have preserved the barrel.  It cleaned up so well the grooves are mirrorlike and the lands are all sharp.  I think someone found it in a deceased relative's belongings and fired it until it would no longer cycle, then ditched it.  I got a good deal on that rifle.

I had this happen once with a chrome bore. (Honest, it wasn't MY fault)  I used Kroil, MPro7, Hoppes, brake cleaner, and CLP--no luck.  I had priced a new barrel and just about given up and then sprayed the bore with Liquid Wrench and left it overnight.  Shiney bore, good as new, no damage. I am not sure if it was corrosion or laquer, but it was brown like rust. Forgot to mention that there was a bunch of scrubbing with a brass brush involved in all of the process too.  The build-up was so bad a new .223 milsurp brush would not go down the bore at first. YMMV.

Just oil and clean the barrel, then blow the rust out of that sucker with 2-300 rounds. [uzi]