I have two Williams FP sights, one that I have had for about ten years and one recently obtained. The newer one had a aperture larger than a like (about .120"), so I tried to swap one from my other sight but it wouldn't screw in. Also another FP aperture I have wouldn't either. The aperture from the newer sight does screw into the other sight but the threads do seem a little undersize. Did these sights come in two different thread sizes. All three of my apertures seem to be the same TPI. Also, checkering on apertures are different, my two from my first sight have crosschecked "lines" while the newer one are "V" cut crosschecked like found on Marbles apertures or on rifle stocks. Not sure what I have here. Any thoughts (if I didn't totally confuse you).
Thanks,
Dave.