Wouldn't make sense.
See, combat loads are either slugs or buck. Slugs max out at 1 1/4 ounces or so.....and don't take up lots of room, so a 3" shell is redundant.
An ounce of lead at 1300 FPS is and ounce of lead at 1300 FPS regardless if it came out of a 2 3/4" shell or a 3 1/2"
Buckshot is made up of large pellets.....and the # of pellets in a 2 3/4" combat load represent the maximum weight payload....and since that payload fits in a 2 3/4" shell, going to a 3 1/2" would just mean you have more shot buffer.
Besides, hunting loads with large paypoads are meant to reach out further, in a combat round you are dealing up close and lower recoil will trump longer reach revery time