I know a lot of people have always been curious about adding sights to an H&R or other single shot shotgun. Lots of people have wondered how H&R made the Buck 162 with peep sight, despite nobody seemingly wanting to drill and tap any other 12 gauge version. I always assumed they had used some kind of trick to make it work. The way they are mounted makes it look like they might have drilled and tapped at an angle to allow more metal to work with.
Back in the fall I was digging around in my safe and I found an H&R Buck 162 I had bought about this time last year and completely forgot about. I've never even shot it. I decided to see exactly how the sight is mounted. As it turns out there is no magic going on. H&R drilled and tapped straight over the chamber at about the 9 o'clock position. It's just two small screws, no epoxy or anything like that. There is not extra metal. It has exactly the same chamber thickness as a Topper model. They did not drill all the way through to the chamber.
I thought people might want this info if they were looking to add sights to another single shot 12 gauge where they are worried there is not enough metal to drill and tap. There is, but you would have to be very careful doing it. I see no reason you could not mount a Skinner peep sight to one. You could probably use a reflex sight. I would not mount any kind of scope to one.