The webs at the breech are 1/16" thick on my Bucks County builds and the purchased pin drilling jig , even after a lot of "fiddling around", wasn't accurate enough and took way too much time. W/ the drill press setup shown, 4 drilled holes in the bbl lugs takes 15 mins and slightly less for the 3 RR pipes...all holes are drilled through in one swipe. The time does not include the hole layouts.
Parallel clamps are used at each location and after the first hole is drilled, a music wire pin is pushed in and the clamps are moved to the next location and then that hole is drilled through. The hole nearest the muzzle is done when the setup is turned around end for end.
The pin holes for the TG and the trigger pivot are also done w/ this setup.
If these pin hole drilling jigs work for many builders, that's a good thing....I found that they weren't for me for the above reasons...Fred