BR is correct, I just pulled and measured the front sight screw from my grandfather's original Krag and it does measure .156 diameter and 30 threads per inch more or less. The imperfect dies they used back then produced "drunken" thread pitches.



I think I just attached an image. If so it is that screw on an optical comparator. I measured about .101 inches across 3 threads, should be .1 if the threads were exactly 30tpi.
An 8-32 screw's theoretical OD is .166, because the threads have tiny flats on the peak even the best quality screws will mike a few thousands smaller.
Measuring with thread pitch diameter wires, I got this
8-32 over wires .1875
.156-30 over wires .1865
Even though there is a large difference in ODs the large radius on the crest of the Krag screw means its theoretical OD is larger than measured. I just checked to see if a krag screw would fit in a precision 8-32 hole and the answer is no. The rounded roots get in the way. It would be very bubba to force it, but it would have been amazingly close.

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