I have an 870 express tactical with the 6 round magazine tube and the 18.5" barrel. I bought a 28" barrel to put on there for the occasional times that i shoot trap. However the barrel lugs are in different spots. Everything else works fine, barrel fits into the reciever fine, foregrips clears the barrel lug fine, action cycles fine. My question is can i make a spacer to fill the gap in between the barrel lug and the nut, so that the barrel will stay in place? I have access to a lathe and im sure i can make it to the correct length. Or should i return the barrel?

 

My current barrel on top, and new barrel on bottom.

 

New barrel on gun.

It's not the long barrel that is the problem, it's your extra long mag tube. A spacer sleeve would take care of the problem, but you would need an anodized aluminum tube of the correct diameter for it to look right. If you don't care about how it looks, your options open up a bit as for materials and look. I would consider fabricating some sort of gasket material so you don't have a metal-on-metal situation. You can always buy an old Wingmaster for about three times the cost of your new barrel and have a shotgun built for what you want.