Tank Projectiles Home Types     When tanks were first introduced there were basically 2 types of shells; a solid shot used on other tanks and fortifications and a high explosive shot used on infantry and light cover. Today's tanks fire a variety of projectiles that can be applied to all sorts of problems. The most common rounds in use today are a high explosive anti-tank (HEAT), armor piercing fin stabilized discarding sabot (APFSDS), high explosive squash head (HESH), and high explosive (HE). Below is a picture of what the US Abrams tank uses (m828, and 829A1 are APFSDS). Image source:https://fas.org/man/dod-101/sys/land/120MMRDS.JPG                                            The Physics       Today's tank guns are not rifled meaning that shots from the cannon do not spin which makes them less accurate. The way to help negate this is to use shells that have fins that deploy after the round leaves the cannon barrel. This then helps the rounds fly straight as well as lessening the drop of the projectile because of the way the air moves over the fins. Think of it like the wings on a plane, only on a smaller scale. Another type of shot is discarding sabot shot. This shell type has a sabot that helps stabilize the shell in the barrel which then falls away after the shell leaves the barrel. Pictured below is an APFSDS shell being fired.     Image source:http://static.panoramio.com/photos/large/29178126.jpg The real physics begins when we start talking about the effect these shells have on their target because each of them utilize a different method of causing damage to the inside of a tank. Below I'll talk about the three most commonly used against enemy armor. The first shell type is high explosive squash head or HESH. HESH does not penetrate the target, rather it impacts. The head of the projectile then conforms to the surface where it explodes, sending a shock wave through the armor and creating sprawling, an effect where the tanks own armor comes apart and causes damage to the inside of the tank. Below is a picture depicting this.                      Image source:http://armoredtalk.com/wp-content/uploads/2015/12/image00.png        The second ammo type is high explosive anti-tank (HEAT). HEAT has a conical cavity with a copper lining and a high explosive charge behind that. When this shell hits, its explosive charge goes off and the cone directs the molten copper into a stream that then penetrates the tank and causes damage. Below is a picture depicting this.            image source:http://www.robinsonlibrary.com/military/artillery/ordnance/graphics/apshell3.gif The third and final shell is APFSDS or armor piercing fin stabilized discarding sabot. This is a kinetic energy shell that relies on brute force to penetrate the targets' armor. These projectiles are often under sized for the gun and rely on a sabot to help them leave the cannon. Once they do they are stabilized by fins until they hit their target where they penetrate the armor and cause damage.