It looks like an ordinary bolt that has been modified with a grinder. Too aggressively by the burnt metal. Er heat treatment L. O. L.
Since it is actually a tap; you probably are OK for anything you want to use it for... I personally would just tap a test hole to check fit of a plug/etc. before actually using it on a part..Do you have enough room to run the tube on a steady; and run the tap in with a tailstock center? I have done that before on large threads... But if you have the room to do that; you probably could single-point it.. Jesse
Lately I’ve been buying taps and dies as needed from these guys;https://drillsandcutters.com/Don’t know if they are US made, but always seem good quality and they often have some of the oddball threads we encounter with airguns and gunsmithing.