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.
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 must repeatedly remove a small amount of metal and then recheck the groove's width.
Figure 4: Hand filing of alignment groove.
The fit and alignment are now perfect. The noticeable gap in
the chamber and barrel tang is gone, and the barrel now mates flawlessly with
the receiver.
Figure 5: No more gap at the top of the chamber.
Next, we turned our attention to the bare metal. We used a cold bluing process to restore the alignment groove to a factory-finish appearance.
Figure 6: Prepping metal for cold bluing.
Figure 7: Before at the top, after cold bluing at the bottom.