I would do a couple things - scrub the bore down really well - make sure there is no oil or residue in there. Use a copper bore brush and really work it for awhile.

Second, try different primers. I've found that 777 primers give less of a crud ring (more expensive, though) with some of my rifles.

Having said that, IME some rifles just produce more of a crud ring than others, for whatever reason. I have an old .45 CVA that doesn't get the crud ring at all - I can shoot many, many times without swabbing. I have a Knight that I have to swab between every shot because of the bad crud ring, regardless of what I do.

You may just need to switch to another powder....