So I have used Loctite 480 to repair 4 barrel and cap cracks. 3 of them were on the threads. And it seems to work great even when there is tension on the gap from putting a section in. The stuff is black and blends in pretty well with BHR but I just did a red swirl and it is pretty noticeable. The only way I know of to clean it is to use a dental pick, a head loupe, and bright light to pick away at the 408 till the red shows through.
Is there a better way? I would love to chase the threads but is there any tool that can chase multi-start threads?