corrosion at the muzzle

[rdmercer]

I have a Mosin 91/30 that has what appears to be rust in the muzzle area. The rest of the bore looks shiny with strong rifling. I have used a brass or copper wire brush and and a dozen patches using Hoppe's 9. I can't get the muzzle to clean up so what can I use or do to get the corrosion off?

 

[LAGS]

Try JB bore Bright Paste on a tight fitting Patch or Bore Mop.
I bet what you are seeing is Pitting that is Not going to come out.
That is why they Counter Bore a lot of those old barrels that are in that condition.
I sporterize ones that I get without perfect bores at the end, so I am cutting down the barrel and recrowning them
But if you want to leave your barrel as-is, then look into having it counterbored if it doesnt clean up.