Dave, I don't know why I'm trying to acomplish something like this, but like climbing a mountain, some do it just because it is there.
The best shooters with autos run split times around .2. The best will do less. (and that is with hitting stuff) A good pumpgunner will do .3-.4. I've gotten down into the .2-.3 range with a pump. I can do 4 aimed shots in a second on a good day. (need more practice to make sure the good days come more often though).
So what you see is that if you are running a course with lots of chances to move around and the targets are spread out, the pumpgunner can hang in there. But when you start running into arrays of bunch of targets bunched together the pumpgunner starts to lose fractions of a second every time. (the other time we start to give up time to the auto shooters is when we need to shoot from contorted positions, prone, squished up on weird barricades, in tunnels, that kind of thing).
I just want to get an 870 as slick as possible. Lots of weight up front, (where did I leave that weight bench?) and a high ammo capacity. When you are trying to shoot 30 rounds in 40 seconds every extra shell helps! I figure the extra weight will keep the muzzle down a bit more, but I'm giving up lightness on the swing. However I figure the extra rounds will offset that as going head to head against a guy with a 9 or 10 shot Benelli and me with my 7 shot 870 means I get to spend an extra second or two loading.
Aww heck, a 30 inch 870 on me looks like an 18 inch gun on most people anyway.
I might as well try to milk the size advantage.
I'm also going to put a 3 gun gear side saddle on it, as well as my standard nylon butt cuff. I'm giving some serious thought to adding some sort of flip up rear sight leaf on the rib to facilitate 100 yard slug shots. I've seen some comp guns from way back when set up that way. I could go ghost ring sights for the precision on slug shots, but personally I think nothing beats a good old fashioned bead for what the shotgun is best at. Close and super fast, plus every now and then they like to throw some clay birds at you.