I had previously posted some information and photos under the topic My first Krag. Everyone was very knowledgeable and helpful regarding my Krag. One member pointed out that the rear sight screw on my 1901 sight was not correct. I was fortunate enough to find an original screw which I received today. I’m posting several photos showing the dilemma. The tapped hole and screw diameter of the existing (incorrect) screw is too small compared to the one I received (which appears to be the correct screw). Can someone verify I received the correct screw? If so, should I leave the existing screw in there as it must be an original configuration? Should I drill and tap for the larger diameter (correct) screw? Thoughts, comments or opinions?

ADDING THE BELOW INFO

I labeled the 3 screws

1 - This is the front screw that came with the Carbine. I believe it is period and correct. There are no problems with it and it sits correctly in the recessed hole of the sight.

2 - This is the rear sight screw that came with my Krag Carbine and 1901 sight. I don’t know if it’s period and I’ve been told it’s not correct for a 1901 rear sight screw. The threads are clearly thinner than the other two screws and there seems to be unusual wear on the threads. The head on the screw is too wide to sit down into the recessed pocket of the 1901 sight. It does appear to hold the sight on tight.

3 - This is (I’m told) a period correct, not a reproduction, rear sight screw for a 1901 sight. The threads seem to be about the same size and pitch as the front screw which makes me believe it is correct. It will sit in the recessed pocket of the 1901 sight which also leads me to believe it is correct. The threads will not engage with the tapped hole.

Thank you,
Mike

Modified the original post to include description of screws. Let me know if additional photos or angles would help.

I plan on shooting it, but would like to keep it as original as possible. It appears to be a legit 1899 carbine with a period replacement stock. I believe it may have gone through an arsenal rework as an engineer carbine. The current screws hold the sight firm in place. Here’s a link to my original post with lots of pics:

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Mike

#2 is not right. #1 is correct and #3 looks correct too. 
No disrespect meant towards you but my advice is take it to a professional gunsmith or machinist who knows what they are doing. Little room for error here, barrel steel is soft and I believe that's an original $$$ barrel.

I have one inclination to keep using the screw that came with it. By chucking on the threads one could turn down the head so it fits in the pocket. It would look reasonably correct.
My reservation here is the OD portion of that screw shows wear.  If it is just catching by the points of the thread it may strip if too much pressure is applied.

Redrilling a new set of holes just forward or behind the originals could be a solution if yours was not so potentially collectable. The hand guard would not fit the sight if this is done.

Building a forming screw/tap to displace the metal to something resembling the original threads is the other option I see. Working with this barrel, it could go wrong as mentioned in my first reply.

Whether the CMP could re-barrel it to carbine specs and not lose collectors value I will let others weigh in on this option.

On that first solution I could do it in 5 minutes with the screw and sight in hand. Others have reduced head size by chucking on the shank with a hand drill and filing. I would not recommend this as the chuck jaws may damage the outside of the threads and cause a marginal fit to strip. If you have a local machine shop that has the right size collet it would take them no longer that it would take me to do it.

Spent a little more time on the threads and was able to seat the screw flush with the base.

FWIW: I think you did a great job!  Well done!

Thank you all for those very kind and generous words. I feel I’m the fortunate and temporary keeper of this and other historically significant arms. While I enjoy shooting them all, I do my best to also keep them original and/or make them whole again.

Now, I have to admit I soiled my pants a little on this one. There was a point when I was working on it where the new (correct) screw wouldn't go in, but the old (incorrect) one wouldn't bite anymore. That's when I wondered why I do the things I do. Thankfully I’m pleased with the results and it all seemed to work itself out in the end.

My buddy finished 60 rounds of his special target loads to get me started. Heading to the range on Monday to finally see how she does. Hopeful that after all this, she shoots straight.

Mike