Next up, Fallout weapons converted to D20.
Rate of Fire: Some ranged weapons have a rate of fire of 1, which simply means they can be employed once per round and then must be reloaded or replaced. Firearms, which operate through many different forms of internal mechanisms, have varying rates of fire.
The three possible rates of fire for handguns, longarms, and heavy weapons are single shot, semiautomatic, and automatic.
Single Shot: A weapon with the single shot rate of fire requires the user to manually operate the action (the mechanism that feeds and cocks the weapon) between each shot. Pump shotguns and bolt-action rifles are examples of firearms with single shot rates of fire. A weapon with the single shot rate of fire can fire only one shot per attack, even if the user has a feat or other ability that normally allow more than one shot per attack.
Semiautomatic (S): Most firearms have the semiautomatic rate of fire. These firearms feed and cock themselves with each shot. A semiautomatic weapon fires one shot per attack (effectively acting as a single shot weapon), but some feats allow characters armed with semiautomatic weapons to fire shots in rapid successions, getting in more than one shot per attack.
Automatic (A): Automatic weapons fire a burst or stream of shots with a single squeeze of the trigger. Only weapons with the automatic rate of fire can be set on autofire or be used with feats that take advantage of automatic fire.
Reloading a firearm with an already filled box magazine or speed loader is a move action.
Refilling a box magazine or a speed loader, or reloading a revolver without a speed loader or any weapon with an internal magazine, is a full-round action.
Loading a belt of linked ammunition is a full-round action. Linking two belts together is a move action.http://www.systemreferencedocuments.org/resources/systems/pennpaper/modern/smack/weapons.html#rangedweapons