Ok, so I had some more free time today and tried out some of the same loads except this time using a Remington 870 with a Kicks Buck Kicker choke on a 28" barrel. All shots were 40yds.
Remington 3" 00 15 pellet
13 pellets in a 10" circle and the other 2 pellets missed the 10" circle by about 2".
Winchester 2 3/4" 00 9 pellet
7 pellets in a 10" circle and the 7 pellet group measured 6"x4".
Remington 2 3/4" 00 9 pellet
7 pellets in a 10" circle
Remington 2 3/4" 000 8 pellet
6 pellets in a 10" circle with 5 of those in about a 4" group
It looks like the Remington buckshot loads are going to be the way to go especially in the 3" 00. I was amazed at how tight of a pattern it was holding. I guess the 870 and the Browning Auto 5 both shoot the Remington shells extremely well with the upper hand going to the 870. The only downside to the 870 is the recoil is brutal with the 3" loads.