Maybe a 100 years ago when barrels were soldered together by hand there might have been some miss matched sets but today, you are wrong in your thinking.
Go to you bench and set a target at ten yards and shoot it with two Winchester AAs of 9 shot, and you will find one hole of about one inch in diameter, if not then the chock tubes you are using are junk, and if you still don't think its the tubes, then simply switch the tubes to the other barrel. you will be surprised !
