I haven't found a mod for a shotgun turret that's been done well yet. I think this would fit the mod theme well, and also give players a reason to automate shotgun shell production. I think shotgun turrets would act good as front-line defenses obviously with shorter range but maybe with higher rotation speed and health to offset.

In that same vein, shotguns are known for their flexibility and utility due to the different types of shells you can load. A couple of extra ammo types would do well to actually make the pump shotgun useful as well as let you customize shotgun turret mechanics a little bit:

-Frag or Airburst HE shells that deal small explosive damage.
-Slugs that act as miniature cannon shells with small pierce, maybe even knockback or stun if that's possible.
-There's already a cool incendiary ammo mod out there (https://mods.factorio.com/mod/IncendiaryMunitions), but Dragon's Breath shells that deal small fire damage & set targets on fire would go well here too.
-Some kind of poison variant of a slug or needle-cartridge kinda thing that deals damage over a longer time, maybe good for tagging worms with and then running.

Oh, funny mention about the above IncendiaryMunitions mod; it doesn't play well with this mod. At startup:

'Failed to load mods: Error while loading entity prototype "molotov-cocktail-stream" (stream): particle_horizontal_speed has to be greater than particle_horizontal_speed_deviation'
Modifications: KS Combat

Figured I'd report that instead of spamming threads.

Thanks, I have fixed the error

Shotgun turrets, would be cool, would need to se about graphics

In regards to graphics I've always thought the default gatling gun turrets would work pretty well for a shotgun turret. Replace the ammo belts with a belt of shotgun shells and then make the barrels smoothbore- you've got yourself a bonafide beefy automatic rotary cannon. If you're wanting unique graphics for this I would still start with the default turret as a base.