It appears to be an ordinary sawn-off double-barrel shotgun, but the Scout (or someone else) cleverly modified the weapon to hold more ammo (3 times more ammo than ordinary double-barreled shotguns,which is 6) and also turned it into a lever-action shotgun.
Like the ordinary pump-action Shotgun that other classes use, the Scattergun excels in close quarters but does a horrible job at long-range combat. Also, the Scattergun has a slow reload since it isn't magazine fed, as the weapon's internal magazine has no opening large enough to put magazines through.
The Scattergun's deadly at point-blank range, as the damage ramp-up is 175% instead of 150%, letting a Scattergun deal 90-105 damage at point-blank range. The Scattergun is generally bad after point-blank range and medium range; after that, the Pistol is a better choice. This weapon's first reload takes 0.76 seconds, and the reloads after that take 0.56 seconds, unless you shoot again, in that case the 0.76 second reload will take place again. A full mini-crit shot can take out 125-health classes in a single shot. Mini-crits can be dished out forcefully for 8 seconds by drinking the Crit-a-Cola. However, you'll take 10% more damage during the boost.