I am having a heck of a time getting my CVA Optima clean. I've tried a bunch of things. All the stuff CVA sells in the cleaning kit... hot water... hot soapy water... even acetone. I can't get the powder residue off of the area at the bottom of the barrel... I've been using the 777 50 grain pellets. I am switching to loose powder next year as I think the pellets really make the gun dirty.

Any ideas how I can get this clean?

Thanks