Getting ready to make an adapter to mount a American tang sight on an Martini 12. The "tang" has two 8-40 holes drilled for a Parker Hale sight at what looks like 70 degrees radial. So that fixes the primary mounting holes.

The gap that has to be filled is 1" long so the tang sight has to be shorter than that.

The question is what tang sight would be best and what are the mounting hole specs? The Lyman no 2 for Marlin 336 has .845 hole spacing but they don't tell you the threads on the two mounting screws and I don't have one at hand. Varner makes a sight with a 0.5" hole spacing and 10-32 screws but the sight base is actually about an inch overall length.

As for the angle of the tang vs the bore, I am not sure and hard to measure. By eye it looks comparable to a Win 1894.

Any suggestions as the a good sight to go with? And the corresponding drill/tap size?

Russ, I do not know the specs, but this Marbles tang sight comes with either a one screw hole or two screw hole base. The one hole base works fine on my Miroku made 1886 a shown in the picture. The little bump just forward of the base is the tang safety.

Thanks for that. The Varner sight base is longer than 1" so that's out. The Win 1894 has longer hole spacing so the base is very long. There is a Marlin sight that's sort of generic with short hole spacing. Perhaps that's the ticket.