870 and 3 1/2 shells
I just picked up a 870 express super magnum receiver with the trigger group feed tube and slide, basically everything minus the barrel, forend, and buttstock. Now this receiver takes the 3.5 shells but I wanted to put the mossberg 18.5 standoff barrel on it but it only comes with a 3 in chamber. Do I have to get a barrel specifically for the 3.5 shells or can I have a 3 bored to a 3.5. I know I don't need a 3.5 but that is what I want so if anyone could help me out I would appreciate it.