I have a Uberti 1873. I want to mount a Pedersoli tang sight on it. The question I have is, is it necessary that the rifle’s tang screw be used in the rear hole of the sight? This would require getting another screw that would be longer with a small head to fit into the mount.
Or, just move the sight forward enough to clear the tang screw, then drill and tap. A question that I have with that, is with the forward screw hole, will there be enough metal there, so as not to weaken the metal enough that it might crack?
Thanks for any and all input.

Sir I am no authority but have seen on Taylor arms with the 1885 they make a longer screw for it.

I can look at my Cimarron 1873 when I get home, but I'd be worried about having the tang sight that far forward but still with enough clearance that the bolt and hammer won't touch it.

http://www.marblearms.com/universal-rear-sights.html

Towards the bottom of the page is a chart listing screw sets, including your rifle. Although they are for Marbles tang sights the lower screw will be the correct length, diameter and threads for your Uberti.
I looked at the Pedersoli website and could not find screws.

Thank You all for your help. I can make it from here. Thanks.