I was looking for a cheap truck shotgun, so I picked up a Hawk 982, a ChiCom clone of the Remington 870, for $200 at a gun show. It's got GR rear sight and a kind of tall front sight, which I didn't care for. I really wanted one of the clones with the rifle sights bit didn't see any at this show.
As fate would have it, Midway had a Rem 870 barrel, IC, RS on sale for $114 (dealer price). So I said, what the hell, I'll get it and help support Larry at the same time. I figured it would be a direct fit on the Hawk.
Wrong. The barrel ring on the Remington barrel is farther down than the one on the stock barrel. Other than that, it fits. I solved the problem by turning a piece of 1" ID PVC tube down until the wall thickness was a couple of millimeters, then cut it off to 3 3/16th inches to make a spacer. Put on the Rem barrel, put the spacer on the mag tube, and screw down the cap. Voila, she is finish.
I'm eventually going to replace the PVC with a piece of 1" ID seamless tubing, just gotta find a small piece someplace.