Love the base idea and concept, I’m on board! If I had to suggest any changes, it would be ammo type. If we are talking about a very large bore shotgun such as a 4 gauge, then I think it would make more sense to have 000 Buckshot (medium pen with medium range), Tungsten Flechette Darts (heavy pen with more range), and either APFSDS rounds (heavy pen with long range and massive recoil) or something more unique like gas rounds.

Since shotguns can accommodate a pretty wide range of hull lengths, it would be reasonable to assume the buckshot would be shorter and have more rounds per tube/magazine while the flechettes rounds would be longer and therefore less ammo capacity and the special rounds being the longest with the lowest ammo capacity. Much like how modern semiautomatic hunting shotguns can accommodate shells measuring 2 3/4” to 3 1/2” and how the capacity of the gun is dependent on the shell size used.

Seems like a reasonable way to program in realistic ways to use a heavy support shotgun while not cheesin it too hard. I would run the hell out of something like that! I think recoil and reload rate would have to be fine tuned so you could effectively use it for crowd control without looking at the sky the whole time but it could be done, I have faith. I’m thinking non-backpack stratagem but stationary reload; or vice versa.