I loaned a spare muzzleloader out to a friend of mine just starting out hunting last year. I told him take it home practice with it and see how he likes it. I got it back recently and it doesn't look like he ever cleaned it even though I explained it to him and showed him how. After getting last years load out which was a pain in the ass I gave the gun a major douching wash rinse repeat many times over. I took a wine cork to the grinder until it would fit in the end of my barrel and filled the barrel with solvent to help breakdown the heavy stuff. The barrel is nice and shiny now but looks like it has a bit of pitting. I haven't had the chance to shoot it to check for accuracy due to the weather so I thought I would post my question here. I'm thinking of sending it down the road to another friend but dont want to sell him a lemon

Irving, I had pretty much the same thing happen to a TC Omega. After finding a recipe on line for "Murphy's mix", 1/3 murphys oil soap, 1/3 rubbing alcohol, and 1/3 Hydrogen pyroxide, I scrubbed the barrel with this mixture. Then i put a toothpick in the breach plug hole, and filled the barrel with the mixture and let it sit for a few hours. This mixture will fizz and foam, and remove any rust left in the barrel. The barrel cleaned up very nicely, and it shoots as good as it ever did. After making scope adjustments during the first 5 shots, my last two shots were 1" high and touching each other. I was considering buying a new ML, but not now.

Accuracy issues will depend on the kind of shooting. Sabots, slugs, and patched round ball are impacted differently.
If it were me, I would be using some lapping compound to minimize the pit depth. The catch 22 is pits hold corrosive particles, and they create opportunity for more corrosion. So a bad barrel often gets worse. Lapping can minimize future corrosion.
Lots of cleaners work, but stuff like ballistrol has a basic PH and it neutralizes acidic compounds found in black powder. Again depends on your powder.
Salts found in many soaps are also bad. Good idea to use simple green because it is salt free. Don't want salts trapped in those mini pits.

shouldn't effect accuracy much just ability to get perfectly clean due to the pitting.. Ive got a couple Knight rifles I bought dirt cheap due to neglect, both look like a log chain was dragged thru them.. but both will shoot into a 1.5 inches at 75 yds or better, bad thing is you have to swab every shot or sabot is very hard to get down barrel.. takes forever to get clean also, minor pitting wont hurt as long as you clean/oil well if not it will keep getting worse.

Great advice thanks how is the lapping compound applied

Wrap a brush with a patch and apply the compound to the patch.

You never said what kind of muzzleloader, roundball traditional style you just apply lapping agent to your patches and shoot normally, usually 10 to 15 shots will smooth the pits sufficiently to make it easy to load and clean. Pits at the muzzle crown are a disaster. If this is a modern gun designed to shoot sabots...I know nothing.

Once you get it clean would Dyna bore coat fix it permanently? Ask Mule Deer

Best solution offered yet.

It's a traditions accura inline thanks for the help

I have a cva inline a youngster gave me. He shot it about ten times and then had to fight to load it( imagine!) So he just stuck it in the rafters of a open carport for 4-5 years . The bore is a poster child for the term sewer pipe. It shreds a cleaning patch on a jag. I brushed it until i went blind and got nowhere.
Gave up on seeing shine. It shoots round ball into 1.75 at 100. It shoots bullets with a wad under into 1.75 at a hundred. I now just clean the best i can and when the erosion gets too bad i will bore it to 54. R

I have read many times the barrels are still accurate , however, they dirty up a lot faster.

without a doubt, i can never get a clean patch out of that cva.

For a badly fouled and pitted bore a trick I have used with success is to wrap some 0000 steel wool around a used bore brush and soak it with Kroil. Brush it for a while and then clean with dry patches. Repeat the process until the crud is mostly removed. My Grandson had a guy give him a CVA muzzy that had set for a few years uncleaned and still loaded. We pulled the load and used this process to get it going. It shot well enough to hunt with at reasonable yardage. We did change nipple.
Have a great day.
Jim

Sounds like a plan.

was shooting that CVA inline today with my homebrew blackpowder. shot to 3 inches at 50 yards. i tore it apart and used eliminate on the bore. have seen better looking stuff in a septic tank. finally got a clean patch. ran a patch with ballistol. came out black. scrubbed until i got a clean patch. bore actually has some shine. will see tomorrow if it shoot better. that home made BP surprised me. actually got a crack to the shot with 110g volume. Lord does it make a dense cloud of smoke. think i got about 1% too much sulphur.

I seconds the extra fine steel wool around a bore brush. My guess is that you’ll get it accurate enough to hunt.