mljdeckard, it's amazing just how important fit is. My M1400 Winchester fits me like a glove. My Mossy never did. When I heard about shimming the stock to increase drop (what I knew I needed to get it right), I cut some shims from a pop bottle and lowered the drop of the stock. Now, I'm quite hoping the stock won't beat up my cheek bone anymore. I no longer have to crawl the stock to get a good point. I just throw the gun to my shoulder and it aligns itself, AMAZING! You don't have to pay big money to custom fit your gun if you have a little initiative.
My new Remington Spartan SPR220 was short, not enough length of pull. Now, it's a 20 gauge and doesn't really kick, but I stuck a slip on pad on it and it made a world of difference. Shot it last weekend on doves, points natural, great fit! Today, I stopped by a sporting goods store in my rounds and picked up a Pachmayr pad to fit to it, brought it home, broke out the disk sander, and fit it to the gun. Did a pretty decent job of it, too, if I can brag a little on myself.
Now, all three of my primary hunting shotguns fit like a glove and I'm quite happy with 'em.
Between the 870 and the 500, fit is not a big deal to me. I will MAKE the gun fit if it doesn't. Either can be shimmed and, in fact, there are shim kits made for 'em, or at least the Mossberg, to use if you don't wanna do the pop bottle thing. I just couldn't see spending 20 bucks on a shim kit when I could do it with pop bottles the cheap way.