To Camdog and lavaca,
You both say that you have installed the Talley peep sight and like it.

How did you know the Talley peep would fit your front sight? Did you have to change your front sight?

Why do I ask when I have a scope with Talley rings for the Talley grooves milled into the rib on my double?

Because I like a peep sight for anything other than shooting from a fixed position such as a blind and the express sights on my double rifle work for me out to 50 yards but things get blurry beyond that.

The Talley peep loks like a natural for my double, but I cannot get Talley to provide specs on their peep so I can calculate whether it will work without changes to the front sight.

I bought the rifle on this forum and it was already equipped with the Talley peep. This answer is not much help with your question. Whoever did the work, did it well. The rifle is a Lott and it is dead on at 50 yards.

I love the set-up, it is quick and accurate. I am sorry that my answer is not responsive to your question.

Camdog,
Thank you and it is good to hear how satisfied you are .

Fortunately, one of the online distributors was working this past weekend and provided the measurements that I needed and so today I ordered the peep sight from him. It should be here this week and I am optomistic that it will fit and meet my needs.

Sorry I didn't get back sooner. I've been traveling.

Frankly, what I like about a peep rear sight is nothing else really matters. Sounds crazy, but bear with me a minute. Sure, you can fine tune and make it better, but your eye will go to the center of that sight automatically so the only thing that matters is the front sight.

When I shot the National Match Course, I shot a front blade with a square top that was the exact width of the bull. And, I used a lot of sight black. All that was important shooting paper at 200-600 yards. It's not important here.

The front bead on my .458 Lott is a rather large, ivory colored, round bead. I still sight in for a "six o'clock hold". That is, my bullet hits right at the top of the bead. (some folks "cover" the target with the bead, but I think that is too imprecise, especially with a big bead, which I like.)

It's not the most precise sighting system in the world, but if you simply look through the rear peep and center the large round bead right below where you want the bullet hole to appear, you will do just fine at close range. If it's farther, use a scope or a red dot.

If the shit hits the fan at point blank distances, none of this will matter.