74: Anything less than 18″ on a shotgun is considered a SBS and needs paperwork. 16″ is the magic number for a rifle. Also, you can’t have a shotgun less than 26″ total length so keep that in mind as well.
You have some good suggestions here so I will only toss some suggestions in about optics and leave you with some things I have run into with certain models:
Personally I like the Vortex Strikefire 2 if you are after a dot sight. Other than that, I am partial to my KSG (outside your budget) and my old Mossberg 500 with pistol grip, 18.5″ barrel, and heat shield. It is simple, light weight, with practice you can shoot skeet with it (my son and I do at about a 3/5 success rate most days), and it is really easy to carry. Once empty you can just drop it/sling it and go with your side arm if things get that bad. They are also easy/quick to reload versus many other models like my KSG. I just saw one like mine without heat shield at the used section of Cabela’s for around $350/$400 the other day.
Here are a couple models I have had problems with personally (and can think of off the top of my head):
Escorts – pretty much any one I have ever touched. Don’t know if it is just my luck or what, but I have had nothing but problems in the field with them. I just have never found one that didn’t break on me while hunting.
Police Remingtons: For whatever reason they take a “special” touch to operate. It was almost like I had to go slower when ejecting the shell than when I racked a fresh one or it jammed. I just couldn’t get the “feel” for it versus all other pump shotguns I have used. Probably a special technique that this user couldn’t get down.
Weatherby’s: They look nice, but the feel just wasn’t there. The angle on the stock seemed a bit off (like the Benelli) where you had to put the butt higher on my shoulder to get a good bead down the barrel. Like my Benelli I use for waterfowl, it can be overcome with slight modifcation to position on your shoulder. Just something to be aware of. The operation of the firearm was fine, however.
Benelli: See above….. The angle on the stock is just a bit off so you have to modify things to get the same bead on whatever you are shooting that you have with other guns. Not a biggie, but something to be aware of.
Older, used: Awesomeness….. IF you get one that wasn’t beat up. I had a Model 12 growing up that I loved and it worked great -> as long as you lubed up the action after every 6-8 shots. Otherwise it wouldn’t cycle correctly. It was just old and needed some gunsmithing love that I was too cheap to pay for. Just be aware that things like that are common with older guns, which makes them all the more awesome in their own right. Also had issues with a few older Ithacas and Brownings, but they were “well loved” in their day and needed work. Just be careful of used to make sure you don’t get one that is almost worn out.
Again, I am sure that there are some total gems in that group I just tossed out. Other than the Escorts, I would say that nothing that would be a “show stopper” for any shotgun. It would just take some practice with certain makes/models. Again, this is just based off my experiences which are mostly hunting related.
Someone you might want to hit up is Flatlander. He has messed around with a lot of tactical shotguns in different situations (other than hunting situations).