Thread size for aperture of TC peep sight?

[Bill M.]

Does any one know the thread size for the aperture in the TC Hawken peep sights? My measurements come out to it should be a #12-40. Does anybody have a source for replacement apertures for these sights? Is it metric or SAE? I did not find any metric sizes close. It is the compact, low sight. Not the real tall folding one.

 

[Grimord]

I have replaced the aperture in my T/C peep sights with standard Lyman apertures with no issues.

 

[kelvinator]

Yes, I have the TC peep, a Mossberg S331, and a Lyman on various rifles, the apertures are interchangeable among them all.