View Full Version : 30-40 Krag rear sight screw thread data?

September 13, 2010, 04:50 PM
Does anyone here know what the screw thread is on the rear sight hold down screws?

A friend of mine has brought me a action with a new barrel that needs the rear sight installed, the screw holes in the barrel are #6-48, the screws from the original barrel measure (over damaged threads) 0.155, which is in between #7 and #8. A #8-40 screw won't fit thru the rear sight screw hole. The thread on the original screw appears to be 30 TPI (hard to tell, only a few threads on the screw). The rear sight has to be repositioned, and new holes drilled and tapped, to be installed, the sight screw holes in the barrel don't match with the cutout in the rear wood.

I tried tapping a #7-30 thread (I have that tap) in a piece of aluminum, the original screw would not thread into the threads. I don't have a #8-40 or #8-30 taps, but I can get them.

The guy wants to retain the original screws, but if I can't do that I will open up the rear sight base holes to take a #8-40 (I have the screws for that) and tap it for that. I am willing to buy new taps, but would like to get ones that will work with the original screws.

Any help will be appreciated.

This will also be posted in the "Smithy" forum.


September 14, 2010, 03:28 PM
I recieved an answer from Gary Griffiths to my post in the "Smithy" forum, and it has answered my question. Thanks, Gary!!

His post:

Krags have non-standard rear sight screws. Read all about it here:


The guy wants to retain the original screws,

As the song says, "You can't always get what you want."

You'll need to drill and tap the holes for regularly available screws. He may be able to sell his original screws to someone restoring a Krag that hasn't had the original screw holes buggered up.

End quote.

Thanks for your attention.