[MikeSid]

Take your gun template and cut the shape out of a piece of 3/4" x 10" hardwood. Taking the interior cut away piece, attach thin gauge 1" metal strip molded to the perimeter shape. You are making a cookie cutter with a solid interior piece for stability.

Next take the scrap piece of hardwood with the gun cut-out and clamp it to the interior pages of the book - with the cover and several pages open. Then place the "cookie cutter" back into the scrap piece with the "blade" down. The kerf of the cut in the hardwood will allow room for the metal strip "blade".

Place the entire apparatus into a hydraulic press and press the blade through the pages. You'll only get 1/4" cut each time so you'll need to make 6-8 passes. And you'll have to manually remove the cut away pieces from the cutter, but your cuts should be consistent. And at a 1/4 inch each time, the blade should not deform and would be held consistent by both pieces of hardwood.

As a practical matter, this might be a complete cluster, but in my mind when I watch the Shawshank Redemption, this is how I envision the prop guys doing it.