butlersrangers wrote on Oct 5^th, 2018 at 12:57am:

Per Franklin Mallory, "Krag Rifle Story", 2nd edition, page 210, Appendix 9, the large screw, for the original type of model 1892 butt-plate, had a convex head. It appears your current screw is of a later type and that a convex head screw would be a nice fit.

Thanks for sharing that drawing.  It does look like that screw would fit.  Now, the challenge of finding one.  I will look for that book as well.