Hello St. George,
I bought my original 1873 Rifle sight from Al Frasca, it is old/new stock, just what you would expect from Mr. Frasca. The problem is, when I sit the sight on the barrel, it is hard to pick up the front sight, in fact, I don't have a decent sight picture unless the rear sight is set on "4". I did specify a rifle sight, and the sight is perfect. Another friend told me to measure the distance from my original Trapdoor rifle, from the front of the receiver to the back of the rear sight and use that measurement to set up my H&R model 1875. I am willing to do that, I really like the look of the gun with the original rear sight. I have also added a wooden pistol grip, checkered, just like the rifle pictured at the top of page 42 of M.D. Waite's book Trapdoor Springfield. St. George, is my sight picture correct, maybe it actually is. Maybe I will just have to lean back to get the correct sight picture, and maybe this was correct back in the 1800's.