HI exactly, to around 35 meters a shotgun is fantastic. As to firepower, remember each time that you pull that trigger you are effectively sending 12 9 m/m projectiles down range at around the usual 9 m/m velocities. Beats a sub machinegun rate of fire with aces. A full load of 6 gives you 72 9/mm projectiles, beat that.
The psychological impact of simply racking the shotgun at night, say in the brush, or along the Rio Grande, is extremely effective, as any Border Patolman can tell you.
It was the preferred trench warefare weapon in ww-1 against mass atacks, . They even stopped incoming grenades in the air by good wing shooters.
It is no accident that most police cars have one on the dash.
NO a shotgun is no mistake under 30 40 meters, but it is not slective among mixed targets, it gets them all.
Don jose de La Mancha