The Beretta 470 Silverhawk is a small gun found in Fallout Tactics.
A shotgun, also called a "scattergun", is a firearm designed to shoot a multitude of projectiles with a single pull of the trigger. This makes it very effective at hunting game, greatly increasing the weapon's hit potential. However, the accuracy and power found at close range diminish rapidly as you get farther away from the target. Shotguns designed for military use are often called "combat shotguns".
This shotgun is capable of firing both rounds at one time. Although this can make it a very devastating weapon, you need to reload immediately after doing this. Besides that, there's no real reason to use the Silverhawk; it's weaker than the starting Ithaca 37.