A customer brought in a Remington 1100 Trap 12 gauge shotgun, and the used barrel they purchased on eBay wouldn't fit. The puzzling part is that the barrel fits on their brother-in-law's Remington 1100, and conversely, the brother-in-law's barrel fits on the customer's shotgun. Figure 1: Misalignment gap at the top of the open chamber. Figure 2: Back of the barrel hitting the right side of the receiver. We quickly determined that the alignment groove in the newly acquired barrel was narrower than that of the factory barrel. This discrepancy caused a misalignment with the receiver, making the barrel tilt to the right and causing the right side of the chamber to hit the outside of the receiver. Figure 3: Barrel alignment groove. After determining the direction and amount of metal to remove, approximately 2mm, we used our gunsmithing precision files to carefully and gradually file away the excess metal in the alignment groove. This process requires patience, as you mu...