I just bought a Colt chrome lined 7.62x39 barrel through the EE.  I've spent 2 hours trying to get it clean and it is still nasty.  I've been using Shooter's Choice, Rem bore paste, and Hoppes lead remover cloth.  I think the crud in the bore is carbon from thousands of rounds of dirty surplus ammo.  Will oven cleaner or carb cleaner damage a chrome lined bore?  Is there something else that will do the job?

I can't speak for the oven cleaner but the carb cleaner should be fine.

I use non-chlorinated brake cleaner to initially wash out the big stuff.

Get some SLIP 2000 725 cleaner. Should help a lot with the caked on carbon.

imho, stay away from the oven cleaner.  It is lye.  Very corrosive.

Brake cleaner should be OK but do not get it on plastic.

Try a more serious bore cleaner like Sweets 7.62 and as far as the carb cleaners go, I use SuperTech 2000 carb cleaner from Walmart. It is a non-methanol based cleaner and is used primarily to rid the bore and rifle of the Sweets, which as noted is a serious bore cleaner.

Note: read the directions carefully and never leave Sweets in your bore for extended periods of time.

Mike

ps - I find cleaning the bore while still warm from shooting (WARM not hot!) makes the Sweets work better as it tends to froth when running the bore brush....

put a heavy coat of solvent in the bore like hoppes, shooters choice mc7, or butchs bore shine and let it soak for a few hours.  Chemicals need time to work. Copper removers like those mentioned by Mr wilsion follow the directions on the bottle, as those you cant soak for long periods of time.

After 2 hours of cleaning the barrel should be spotless. Any chance they were using corrosive 7.62 x 39.

I'm not sure if they used corrosive ammo or not.  It almost looks like pitting in the bore, but every time I run a patch through it the patch comes out dirty.  I thought a chrome lined bore would be pretty impervious to corrosive ammo.  

Try soaking the barrel in FP10 for a few days.  It is a CLP so you can leave in there as long as you like without damage.  It will tunnel under debris and lift it off the surface.  This is done by mechanical displacement, not being dissolved by a solvent, so it takes longer.  I'm doing this right now with a couple rifles that have not been cleaned for longer than I would care to admit.

Just put 2 heavily soaked patches through the bore, then brush with several strokes.  2 more heavily soaked patches and let sit for a while (at least 24 hours, but longer is better).  Come back later and repeat.   I have done this a few times now and the patches continue to come out very dark each time.  Still haven't got everything out.

This method takes time, but little effort since the FP10 does most of the work.  

corrosive 7.62x39mm maybe?

need to SOAK THE BARREL

Mr Wilson has good ideas also

corrosive ammo will destroy any barrel not carred for in sufficent ammount of time.

Maybe you barrel is not dirty, and you are see'n pitting?
worked on a Colt 7.62 that was pulled out of  a river, never could get the pits out! heck6Danomite