How did you mount the rail, in the stock.
I used a Mesa Tactical 8 1/2" (cantilever) Picatinny Rail for a Remington 870 as it was available and the radius for the top of the receiver works well with the rifle barrel, and shortened it to suit.
I attached the Picatinny rail to the barrel with some of that two-sided foam "tape" that's used for removeable coat hooks, etc, and played with it until the flashlight beam was centered with the iron sights. I then hogged-out the front of the stock so it would not touch the rail when the barreled action was bolted into the stock. All that was left was to mix up and dye some Acraglass and butter-up the stock and portion of the picatinny rail that's inside the stock. I masked-off the section of pic rail outside of the stock, and used Kiwi shoe polish as a release agent on the metal. It actually went pretty slick from start to finish.
If I were to do it again, I think I would use two thicknesses of the foam tape. As mine sits now, there's probably 1/16" of clearance between the rail and the barrel - it hasn't been an issue to date, but I think I'd prefer around 1/8" clearance.
