cutting the barrel on an 870
I'm going to be cutting the barrel on an 870. I bought it cheap ($150) and want to convert it into a riot gun type configuration. Aside from cutting the barrel to 20", I will be installing a side folding stock with pistol grip and 3 shell carrier, installing an extended mag tube, and mounting a flashlight or possibly laser to it.
I am not sure about the last part though. How do they hold up to recoil, and hoe secure are the mounts? I would want a pressure switch, is that going to be cost prohibitive?
What other options should I consider? I'm not really into shotguns, I like rifles alot more and I'd like to install rifle type sites, but I'm still throwing that one around.