I did all the ruff work, cut and measure the stub and barrel. I gathered all the product. stub, blank, ejector, mounts, and frame. an SB1 with a small firing pin. He did the machine work and I finished. the holes for the mount were drilled into the stub, .200. There was not enough room to drill into the barrel itself. I just lucked out that the cheap pistol scope I had had a very short eye relief, 9". I had removed the scope from my 657 for it made me nervious with the short eye relief. Broke my young sons glasses and dinged his nose once. I used 2 1" Weaver mounts, 6-48 screws. The Finished barrel dia was .717 with only .153 thikness. With a full length insert, one could mount the scope anywhere but way to heavy for a shorty.