'randyinmv1986' - You have a 'mismatched mixture' of original Krag sight parts.

Your pin is actually for a Krag ejector. (The ejector pin is covered by the Left Side-Plate. The pin is 'notched' so it can be pulled out of its hole in the receiver).

You can assemble a sight from your parts. It will not be historically correct, but, it will be useful.
You have a model 1898 Rifle rear-sight base and a model 1902 rear-sight top.

A model 1902 Rifle sight-base is taller than the 1898 Rifle base and has a different sight-spring arrangement.

(The 1898 sights originally had three sighting notches and the 'elevation curve' of the base was for a faster cartridge, that was discontinued. The sight was also discontinued).

You can make a pivot-pin for your sight from the shank of a nail:

Cut the head off of a slightly 'oversize' nail. (Larger diameter than pin)

'Chuck' the pointed end in a Drill-Motor. As you 'Spin' the nail, reduce its diameter with a File. When it is close to fitting through the sight's pivot-holes, polish and reduce the diameter with Emery cloth.

Cut the new 'pin' to approximate length. (Leave it a bit long). Shape and polish the ends of the pin by spinning in the power drill and using File and Emery. Color the ends with 'Cold Blue'.

Original Krag sight pivot-pins were made from soft steel.

Photo #1 - Shows where your small diameter pin is actually used. #2 - Shows a 'parts sight' I put together using the same parts you have and a pivot pin made from a nail. #3 & #4 - Show a model 1898 base and a 1902 base.

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