!!!DnDBeyond has no option to create a homebrew weapon so this is my attempt!!!
***TO ADD/USE THE SHOTGUN RIFLE ADD THE FEAT AND IT WILLAPPEAR IN THE CHARACTERS ACTIONS***
Single target from range 15/60 at 2d6
Up to 2 targets in the 15ft. cone also take 1d4
Reload(1), Misfire(3), Cost 450gp, Weight 12lbs, Ammo cost 7gp for 5