I had a thought today, and it probably sucks. What would the advantages and disadvantages be of a rotary shotgun. A minigun/rotary cannon arrangement which shoots shotgun shells and/or slugs?
There's no advantages to carrying a rotary shotgun as a small arm.
The advantage of lots of barrels allows a high firing rate and gives the barrels a bit of time to cool between shots. This helps prevent overheating. This isn't an issue with a weapon like a shotgun - it won't have enough cartridges in the magazine to overheat before it runs out of ammunition.
The fire rate, additionally, can be plenty high enough with a single barrel. If you look at real combat shotguns
1 2 3, they tend to have a lower fire rate than assault rifles - they hover around the 300rpm mark rather than the 700-950 rpm of the M4 carbine. A higher fire rate clearly isn't a priority.
The disadvantages are:
1 ) weight. Lots of barrels are really heavy. This isn't great for a close combat weapon. Combined with the weight of lots of shotgun shells, you'll find it'll be an exhausting weapon to carry around. A shotgun is a close range weapon - so it needs to be manoeuvrable. You could decrease weight by reducing barrel length, but that also decreases accuracy and power.
2 ) something has to power the rotation. While gas powered rotatary cannons do exist, generally they're electrically powered. If so, you've also got to lug around a battery as well. That ties into 1). If you want it to be gas powered, it's... debatable whether the
3 ) accuracy. The faster the fire rate, the harder it is to control the recoil.
4 ) maintenance. A rotarty cannon, by definition, has a lot of moving parts. If your gun is broke, it ain't a gun.
To sum: a huge amount of additional weight for no actual gain.
If you want it to be a crew served weapon, ala the
XM214, you have to consider again the fact that shotguns are primarily short ranged weapons. A crew-served weapon is not ideal at short ranges. Even if you're shooting slugs, you won't match a machine gun. The weight issue still applies, as well, just to a lesser extent.
It'd be better just to stick to a machine gun. Tried and tested.