Looks like I can't reply to your pm until I have 5 on my post count.
I bought my 500 combo 20 years ago. I don't think they had rifled slug barrels or cantilever scope mounts at that time. So I'm shooting a smoothbore and I bought a slap on scope mount. So when I use the gun for turkey, etc. I either leave the scope on, or have to take it off.
I'm down between Delaware and Marysville, but I'm working in Findlay. Not much to trade. What would you need for the barrel and scope? What is the make and power of the scope?
I'll check when I get home on what the make of the optic is, If I remember right it was a decent scope, it was made for shotgun / muzzleloader, I'll measure the the barrel length as well. I haven't been on this in a little while the forum so sorry I missed your note.