There is some really cool stuff coming out of the gun industry. One of which allows you to mount a 12ga upper onto an AR-10 lower and feed shotgun shells through the magwell from a detachable magazine. Their full sized shotgun came out last year but they started selling shorter barrel versions this year to mate to your virgin AR-10 receiver project as a stockless title 1 other firearm or your sbs lowers.

Prices are a little crazy but if this is the future I'm excited. Can't wait to see these become the new trend because some of the dedicated AR shotguns out there just don't do it for me.

Here is their 12ga "firearm"