Several people on this board recommended using J-B Weld to attach rear sights to shotgun barrels that are too thin to drill and tap. I made a good, accurate 24" slug barrel for my 870 by bobbing an old 28" plain barrel, soldering a Williams Shorty ramp at the front end, and J-B Welding a Williams Guide Open sight base to the rear. Sure enough, it has stayed put through 50 or so rounds at the range. I worry a bit about temperature changes causing it to let go in the long run, but so far, it's as tight as if it was attached with screws.
I have often thought about using J-B Weld to attach a Williams Guide aperture sight to a 28" NEF shotgun barrel, and soldering a Shorty ramp on the front. The Pardner with a 28 barrel is shorter than my 870 with a 24". It would make a very handy smoothbore slugger. I've tried Remington 1-ounce Sluggers in my Pardner, and they do kick a bit . . .