By the way, for the guns you specifically mentioned:
Remington 870 - see my above post. I think this is the best option, hands down. They are made in the USA and parts support is second to none. They have made over 11 million of these to date, for a very good reason. Some newer guns have plastic trigger guards, which is not a big deal, but be ware they come in either plastic or aluminum. Both types are robust and heavy-built. As a side note, these all-steel guns have more refinishing options, such as bluing, than the aluminum receiver guns below which are anodized. For those guns, to re-finish, you would need to look at something like paint or cerakote.
Mossberg 500 - the "other good american pump". These have aluminum receivers, which might matter if you shoot 40,000 rounds through it. Practically, it will be fine. The biggest differences are the top-mounted safety, which works well, but is a PITA if you want to use a pistol grip stock. Some mass berg variants are single action bar, which some people thinks make them pump a little less smoothly than the Remington variants. I doubt most people will notice or care. Also, most modern variants have a plastic trigger guard that is not as robustly built as the Remington plastic trigger guard. If you go with a Mossberg, check a few out and make sure you buy one with a trigger guard you think will stand up to the use you are planning.
Weatherby PA-08 - these are made in Turkey and don't have a lot of aftermarket support yet, but spare parts seem to be obtainable. The design and control layout share many similarities to a Remington 870, including the bolt design, but they are not parts-compatible. The receiver is aluminum like on a Mossberg. They also have not been around long enough to compare long-term staying power in the marketplace and durability compared to Mossberg or Remington. For that reason alone, I would not personally buy one when an 870 is about the same money. YMMV.
Winchester SXP - these are also made in Turkey, but unlike the Weatherbys, parts are basically non-existent in Canada as of this writing. My local gunsmithing shop refers to these as "disposable guns" as the distributor never seems to have needed parts in stock when these guns come in broken, which they told me is a regular occurrence when I talked to them about this last month. These are also aluminum-receivered. I don't have any PERSONAL experience with these, but I trust the local dealer, and he advised to stay away.
Benelli Nova - these are really well made, bullet-proof, and most exposed surfaces are either polymer or polymer coated. On the down side, they are bulky and have a cheap clackety-clack feel to them that does not affect their function. All the Nova's I've used were utterly reliable tanks, but they always felt too big, in almost every dimension, when used in-hand. YMMV.
