I have the exact same set up. Rem 870 with 23" rifled barrel/ cantelever scope mount, and a Nikon 2-7x 32mm scope. Great set up, and I really like it. Very accurate with Hornady SST slugs. Last fall I shot a deer right through the heart at 110 yards while in a tree stand.

I can't help you with your question, I currently have the smooth bore on it, but I have not re-installed the rifled barrel. I always assumed it would go back to where it was. I would be interested to hear from the others.