Canister shot Canister shot ( or case - shot ) is a kind of anti - personnel ammunition used in cannon s . It was similar to the naval grapeshot , but fired smaller and more numerous balls , which did not have to punch through the wooden hull of a ship . Canister shot has been used since the advent of gunpowder - firing artillery in Western armies ; however , canister ( or case ) shot saw particularly frequent use on land and at sea in the various wars of the 18th and 19th century . Description . Canister shot consists of a closed metal cylinder typically filled with round lead or iron balls , normally packed with sawdust to add more solidity to the mass and to prevent the balls from crowding each other when the round was fired . At times when the supply of balls was limited , nails , scrap iron or lead , wire , and other similar metal objects were included . The canister itself was usually made of tin , often dipped in a lacquer of beeswax diluted with turpentine to prevent corrosion of the metal . Iron was substituted for tin for larger - caliber guns . The ends of the canister were closed with wooden or metal disks . Attached to the back of the metal canister was a cloth cartridge bag , which contained the round ' s gunpowder charge which was used to fire the canister from the gun barrel . A sabot of wood , metal , or similar material was used to help guide the round during firing from the cannon . Various types of canister were devised for specific models of artillery field pieces . In 1753 , the " secret howitzer " , a special gun with an oval bore — intended to spread shot even wider — was briefly introduced into Russian service , but ultimately proved unsuccessful . When fired , the canister disintegrates and its shards and projectiles spread out in a conical formation , causing a wide swath of destruction . It was particularly effective during the Napoleonic Wars and the American Civil War , where massed troops at close range ( usually less than 400 yards ) could be broken up by artillery batteries firing canister . At times , particularly at very close range , artillery crews would fire extremely lethal " double canister , " where two rounds were loaded into the gun tube and fired simultaneously using a single charge . Canister played a key role in dispersing the troops assigned to support Pickett ' s Charge during the Battle of Gettysburg in July 1863 " ( see Field Artillery in the American Civil War for more information ) . " Canister shot was also used to good effect by U . S . Marines in World War II at Guadalcanal to break up Japanese Banzai charge s . At times , trained artillerists would fire the canister shot towards the ground in front of advancing enemy troops , causing the conical pattern to flatten out as the balls ricocheted and skipped off the terrain . This in effect widened the killing zone . An example of this tactic was at the first day of Gettysburg , where Lt . James Stewart ' s Battery B , 2nd U . S . Artillery on Seminary Ridge skipped canister shot at Alfred M . Scales ' s approaching Confederate infantry , breaking up their attack and forcing them to take cover in a depression . The canister round is also known as a case ( hence the alternative name of " case shot " sometimes used for " canister shot " ) and is still used today in modern artillery , particularly in the main armament of tanks with smoothbore cannons . The effect is to turn a large - calibre gun on an armoured fighting vehicle into a giant shotgun . This can be used against enemy infantry even when in proximity to friendly armoured vehicles , as the projectiles do not penetrate armour . In addition it can be used to create entry points to buildings , reduce wire obstacles and clear heavy vegetation , as well as strike low flying aircraft and helicopters .