Automatic shotgun An automatic shotgun is an automatic firearm that fires shotgun shell s and uses some of the energy of each shot to automatically cycle the action and load a new round . It will fire repeatedly until the trigger is released or ammunition runs out . Automatic shotguns have a very limited range , but provide tremendous firepower at close range . Design . Automatic shotguns generally employ mechanisms very similar to other kinds of automatic weapons . There are several methods of operation , with the most common being gas , recoil , and blowback operated : Each of these methods use springs to return the retracted parts to their forward positions and restart the cycle . Many automatic shotguns are capable of selective fire , meaning they can fire in multiple modes ( semi - automatic , three - round burst , and sometimes fully automatic ) . Ammunition . They generally store ammunition in detachable box or drum magazine s in order to decrease reloading time , whereas most pump - action and semi - automatic shotguns use under - barrel tubular magazine s . Shotguns are able to handle a wide variety of ammunition , however automatics are slightly limited because the shot must provide sufficient force to reliably cycle the action . This means that they are not compatible with low powered rounds , like most less - than - lethal ammunition . The most common ammunition used in combat shotguns is 00 buckshot , which fires about 9 metal balls and is very effective against unarmored targets . Strengths and weaknesses . A standard shotgun shot fires multiple small projectiles at once , increasing the chances of hitting the target . Shotguns have a short effective range of about , but provide a lot of firepower at close range . Automatic fire enhances these effects , due to the increase in the rate of fire . Automatics typically have much shorter barrels than pump - action shotgun s ( especially hunting shotguns ) . Barrel length contributes to tighter shot spread , so automatics have relatively wide spread . Short - barreled automatic shotguns have a very high chance of hitting close range targets , and can even hit multiple targets in one area , which is ideal for combat situations . Long - barreled pump action shotguns are more accurate and have increased range , which is ideal for hunting and sporting purposes . Automatic shotguns are generally viewed as less reliable than manual operation shotguns , because there are more moving parts and increased chances of error . If any one piece fails , it will most likely halt the operation and cause damage to the weapon and / or user . Automatic weapons are also more susceptible to jamming and negative effects from dirtiness . Use . Automatic shotguns are intended for use as military combat shotgun s . They typically have a high rate of fire and relatively low recoil , making them ideal for engaging multiple targets in a fast paced combat situation . They are able to fulfill several different combat roles , due to the wide variety of shotgun ammunition available . A single gun can be used to breech a door , clear a room , provide support with special grenade rounds , or even suppress a riot with some less - lethal rounds . Automatic shotguns have not seen much use in the United States , but have been slightly more popular in some other countries .