There are many repeating shotguns with through bolts or recoil mechanisms in the stock rendering them unsuitable for bending. Back in the '60's and '70's, the solution was to slightly reduce the thickness of the comb; almost an inverted cheek piece filed from the stock. The proper method of accomplishing this is found in chapter eighteen of Do-It-Yourself Gunsmithing by Jim Carmichel. It's a pretty good book for many purposes; a lot of info for the home gunsmith.