I have mentioned this a couple places, but thought I might put a complete explanation in one place.
The nutshell is that XS makes a sight that is for the fixed front sight J-Frame that is integral to the barrel that requires the front sight to be reduced to a simple post, and the sight glues on with JB Weld. They have it in the small size that comes on the 340 and the larger size:
https://www.xssights.com/Products.aspx?CAT=8375
and you can buy it various places, including Amazon, and I think I did this so it will be the affiliated link:
https://www.amazon.com/Xs-Big-Dot-Tr...r=8-3-fkmrnull
For some reason the instructions are tricky to find on the XS www site. I know they are there but couldn't find them until I externally searched:
https://www.xssights.com/ITEMMEDIA/1...stallation.pdf
The procedure can be summed up with this picture:
The instructions suggest using a milling machine, and on my 638 a friend with one helped me. Clamping the thing was a challenge, you are trying to mill stainless that is screwed into aluminum without tweaking anything, and at the end of the process it seemed like it could have been done easier with files, and that is what I did with my 637. I taped up the parts I didn't want to scratch and painted it with a Sharpie and scribed some approximate lines, and went at it. Here are a couple of in process pictures:
Probably the most difficult part of the whole job is taking the first pass with the file on your perfectly good gun...
When you are done there will be file marks, and used stippling to create a uniform look. You just grind a triangular point on a little punch:
and make a bunch of shallow dents in the surface. Then clean everything with brake cleaner and glue it on with JB Weld, making sure the sucker is straight:
It took longer than I planned, but none of this was difficult.