I bought a Marlin Model 1893 in .23-35 a few years ago and mounted a receiver sight. I could not get the impact down below about 6 inches high at 100 yards. I called Brownells and got their customer service department. The rep recommended a replacement front sight and I ordered the one that he recommended based on his calculations. After I swapped out the front sight, I was able to go ahead and get the rifle sighted in at about 3 inches high at 100 yards. You may have to resort to this, but it is a cheap fix (less than $20 as I recall).
It's a bit tricky to install the new sight, but I managed with the help of a couple of items that I borrowed from a friend who is a pretty good amateur gunsmith. Any gunsmith who works on older lever actions can probably do it for you--it's pretty simple once you have done it.
