Hey Guys, A good friend of mine recently purchased his first Pre Ban AR...since he received it, he's been experiencing some issuses with it. Most of them, I have helped him fix. However, there is one. I need you help with. The gun, from what I can tell, has been shot an TON...I mean a TON. One of the things he needed to replace was the gas rings around the Bolt Assem-the ones on the gun, were almost non existant. He took them off, and put on the new ones...which seem really big. Second, inside the Bolt Carrier where the Bolt is...towards the rear where the rings are, there seems to be a build up of crud.. which seems to be blocking the bolt from entereing the carrier all the way and when inserted, it's VERY tight..I'm guessing this is from the lack of rings. I am wondering how to remove this. Q-tips don't seem to cut it. I was wondering he could use some polishing compound and dremel with a polishing tool? And polish the contact surface where the rings touch the carrier. I understand that you don't want to remove too much material...but...what else could we do? Thanks for you help!!

What you are seeing is a build up of carbon. The best way to get it out is to use a thin steel ruler to scrape it out it is very hard
build up of carbon will wear down the rings so this should tell you how hard the carbon can get
BM

I have managed to remove most of the build up save some at the very bottom. The rings do not appear to be hitting any of the build up just pressing up against the sides. If I put on the one and only  remaining old ring,  it will slided in and out no problem. Comparing the two rings (old and new) I can see very little size difference if any at all. I can post a couple photos if anyone has questions.

Try soaking your bolt carrier in kerosene for a couple of days--just dunk it and forget about it.  It will soften the carbon so that Q-tips are effective.  Sometimes, especially with very heavy buildup, you may have to put the part back into the tank and soak again before all the carbon softens.  Works for me, and kerosene is alot cheaper than the tools offered.  Also, I've turned the kerosene BLACK and it still be effective-it lasts longer as a solvent than you might think.  Hope this helps.

First get the Crud out of the BC with either tool.I use the brownells tool at work and it does a fine job.
Then take a hard look at the transition angle that is cut into the BC that compresses the gas rings.Is it rough?I have seen them look like a Tungsten toothed Beaver had gotten in there and raised hell.
If it isn't a smooth transition,it can raise havoc with the gas rings.

Despite what some may proffer,regular maint. was a consideration the design of the M-16/AR family of rifles,and that includes scraping out the carbon from the bolt mortice in the BC.

For the record,The rifles I am tasked with,see 1-2,000 rounds a week at times,and often I don't see them untill their gas rings get chewed up or broken by the excessive build up where there shuld be a smooth taper in the BC.

Get that crap outta there!

Possibly your bud might be in a position to look for another carrier if the taper/transition is rough.

Gas rings break for two reasons.
Abrasive action caused by the deposits of flash reducing compounds,and bad Metalurgy.

Scrapers are cheap insurance,and invaluable peace of mind.

Best of luck to ya!

S-28

The BC is smooth at the top, then about 1/2 way down it becomes "ribbed". It dose not appear that this was worn down but rather made that way.

Thanks for you all your help guys. I'm going relay this on to my Bro. Big help and many thanks!