I wanted to add a Picatinny rail to my CZ 457 MTR.
Since I don't like standard inserts (low quality) I decided to make my own out of set screws. I started with some 12.9 black set screws but I was not able to drill and tap them so I went with some stainless set screws.
I was able to get a Picatinny rail with a variable mounting hole distance from a Chinese online service ;).
Have fun watching!