It's pretty obvious that the problem isn't the Contender frame since it shoots two barrels well and one barrel not so well. Without knowing what bullets, powder, primer, etc you are using and how the ammo was assembled, it would be nearly impossible to make any suggestions. Either you have a defective barrel (not likely if it's an unmodified factory barrel) or a modified barrel that has a defect. Possibly the ammo is simply not assembled well and you have chosen the worst possible load for the barrel. You also didn't give any info on how "poorly" it was shooting and whether or not you were using a rest or shooting off hand. In fact, you've provided very little info to work with. Can you provide some further information?
