Does you smoothbore barrel have rifle sights or just a bead front? The red dot is probably better than just a bead sight, and you should be able to shoot deer out to about 75 yds with rifled slugs.

I'm not sure which mount you are looking for, some google images show different variations of cantilever style set ups on 1187s.


I would recommend that you find a fully rifled barrel with the cantilever mount permanently affixed for the future. That will get you the best accuracy. With sabot slugs you can double your range.

You may be able to find a used or even a new muzzleloader for the money you'd spend on a shotgun barrel, depending upon their availability.