The 1100 Magnum with a 30" fixed full choke barrel is my favorite buckshot shotgun that I've used, and I've tried a bunch. They are very reliable as long as you shoot 3" magnum loads in them, keep them clean, and replace the o-rings every so often. They are extremely popular in this area and rarely come up for sale. When they do, they seem to command a premium. As mentioned, the barrel only has a single gas port, instead of two on the 2 3/4" models. You can swap the barrel with a 2 3/4" version if you want to shoot light loads, then it'll function just fine. I've also seen people open up the gas port, which will get it working with light loads, but I don't recommend this. If you do this, then shoot magnum loads in it, it'll beat the receiver to death.
The 2 3/4" versions are great as well, but not nearly as popular around here and the price indicates that. They were offered in a variety of different configurations over the years and are good shotguns if they fit your needs. Since you mention buckshot, I really think you'd be better off with the Magnum.
The 11-87 is supposed to be an "upgraded" 1100 that can shoot any both magnum and light loads, but imo it's just the opposite of an upgrade. I wasn't a fan at all of the one I had. My hunting buddy that I hunt with 90% of the time bought one of the Super Magnums and it was a jamomatic. I tried it out some and it was terrible. We also could never get it to pattern anywhere near as either of our 1100 Magnum's. Eventually he gave up on it and went back to his 1100. Several others in our hunt club have also tried them and all of them have ditched them.
