Some more info...
Sorry to bump this but I think I can clarify... The Mossberg 930 SPX is a great gun to start off with. It's pretty much the same thing that Bennelli sells to our troops for a fraction of the price. It's advertised as having a 7 round magazine capacity. I live in Jersey and have seen it a few gunstores with the 7 round mag (stock of course). In New Jersey, dealers are cautious as hell in what they sell. You'll never see anything illegal in the few stores there are. Now, technically, it can hold 7. But it has to be 7 2 3/4 shells and only certain brands will fit. If you ever checked, the length between 2 3/4 inch shells between manufacturers varies quite a bit. So actually, with many, if not most brands, you can only get 6 in. The 1 ounce Remington Game loads can tightly hold 7 shells, but anything longer than those and 7 just won't fit. And if you happen to have various brands of shells and a 3/4 or one ounce Remington Game load, you notice every brand of shell is at least a bit bigger, in some cases vastly bigger.
It tightly fit's 6 3" shells, so if you do the math, It's easy to see how tight that chamber would be loading 2 3/4" shells
Regardless of where you live (within reason of course) as long as you're going to a reputable dealer it's unlikely they'd be selling something that was illegal especially considering the 930 SPX is all stock hardware. I guess you can ask them? Anyway, if it's a big deal just get the 930 tactical. That's a nice gun, especially with the heat shield. It's always fun to "supe up" your own guns but sometimes it's better to buy it that way. In this case, the heat shield, which may or may not be a big deal for you, I really prefer to have, love the way it makes the gun look and if youre like me and shoot alot of shells it keeps the barrel from getting too hot too quick. Second, the 930 Tactical got the "Crusher Barrel" with a mock muzzlebreak that looks cool and gives the gun a nicer look, and has the sharp jagged crusher which can be used as a backup weapon, like a mini-bayonet. Anyway, the point is, you can't get these aftermarket, so do youre research on which model is best for you and keep in mind what if anything you might want to do to it! If you want a heatshield for a 930 I don't think u can even get one through Mossberg. If you wanted the crusher barrel you'd have to shell out for a whole new barrel. You can easily add a mag extension to the tactical and then the only difference between the SPX would be the rail at the top and the sites.
And just a heads up for 930 SPX OWNERS - for anyone that got a 930 SPX with the regular stock you can now buy the same stock on the 930 SPX with pistol grip through Choate. They make the ones Mossberg puts on their guns. Not only does the stock have a comfortable pistol grip, it handles recoil much better than the standard stock. It's only like $70. Get em while u can because they're only making so many cause it just fits the 930 and is meant to give people that bought the original the chance to upgrade to the pistol grip stock.