I'm not trying to come off as a know it all here, or seem simply you aren't doing something correctly, but clean the chamber, throat area. I'm not up on all the terms but sometimes you'll get a build up there between the chamber throat, ( where case neck ends and lands, (rifling) begins. Apologize if this was previously mentioned.Cleaned the barrel, about the same.
Don't get frustrated. You'll figure it out. More than likely laugh about what's going on afterwards. Goodluck