Why do (most) Modern Tanks use Smoothbore Guns?

[Music] this image from the thumbnail shows the prototype of the british challenger 3 the still forthcoming replacement to britain's current challenger 2 main battle tank as you can see the inside of this barrel is smooth a marked departure from the challenger 2's current l30a1 120 millimeter rifled gun this change to a smoothbore gun will bring the challenger 3 in line with the latest variants of the american abrams german leopard 2 and all currently produced russian t-series main battle tanks for those who understand the significance of rivaling it might be surprising to learn how rare it is in the latest generation of tanks for those who don't know what rifling is or why it's used here's a quick explanation simply put rifling is the term used to describe the spiral grooves that run the length of the barrel of many firearms the first rifling process we know about was invented in 1498 but rifled barrels weren't common until the 19th century and didn't become truly ubiquitous until the early 20th the reason rifled barrels became ubiquitous in just about every type of firearm except for shotguns and mortars is because of the tremendous advantage to accuracy that rifling provides as a bullet or shell travels down the barrel of a gun the spiral grooves will cause it to spin this converts a portion of the forward velocity of the projectile into rotation which will continue after it has left the barrel the spin imparted onto the projectile will help to counteract any tendency to tumble something which is extremely likely to occur for any projectile that is not aerodynamically stable a bullet or shell that tumbles upon exiting the barrel of a gun will experience greater aerodynamic drag bleed velocity and tend to veer wildly off target beyond close range rifling solves all of these problems allowing for accurate shots to be made vastly greater distances using conventional bullets or shells this explains why rifled barrels became ubiquitous in almost every military application over a century ago so why have most of the world's modern tanks move back to a type of barrel which became mostly obsolete over the course of the 1800s two words heat and sabos or more specifically armor piercing fin stabilized discarding sapos apfsds for short these initialisms describe two advanced types of anti-tank rounds that came into prominence in the late 20th century as armor technology advanced in the 1960s and 70s particularly with the introduction of the first generation of ceramic composite armors it became clear to military planners and engineers that the current generation of high explosive and armor-piercing shells used by tanks would no longer be sufficient in order to defeat the new generation of armor new types of anti-tank ammunition would be required we'll go in chronological order and assess heat shells first heat is an acronym that stands for high explosive anti-tank a shaped charge weapon that concentrates a super high velocity jet of molten metal to penetrate armor the first use of these weapons was in world war ii where they were used by both the allies and the axis powers primarily as man-portable anti-tank weapons such as the american bazooka or german panzerfaust while the use of heat shells fired from guns was experimented with during world war ii particularly by the germans it was found that rotation such as that imparted by rifled barrels decreased the effectiveness of these shells with the effect worsening the higher the rate of rotation this is because heat weapons rely upon a combination of extremely precise detonation and geometry to form the metal jet that penetrates armor any addition of external forces such as the centrifugal force caused by rotation could interfere with the formation of the metal jet or prevent it from forming entirely given that almost all tank and artillery barrels in this period were rifled and that the commonly used armor-piercing high-explosive rounds were often sufficient to penetrate the armor of the time heat shells fired from guns fell out of favor as mentioned previously this would change during the cold war going back to the start of world war ii shortly after development of the first heat weapons began a new type of armor-piercing round was being researched primarily by the british this round termed apds for armor-piercing discarding sabo followed the development of the first fixed sabo rounds by the french during the 1930s apds rounds consisted of a hard dense projectile of smaller diameter than the bore of the gun from which it was to be fired surrounded by a collar-like sabo which would be sized to tightly fit the inside of the barrel when fired from a rifled barrel the sabo would transfer its rotation to the projectile and upon exiting the barrel fall away decreasing drag while the projectile continued to its target by the end of world war ii these rounds have become quite effective and they continued to be developed in the post-war years becoming a common form of anti-tank ammunition however as apds rounds were improved upon a clear design trend was that the rounds became longer and thinner this posed a problem since the higher the ratio of length the diameter becomes the higher the rate of rotation needed for spin stabilization to be effective past a length to diameter ratio of about six or seven spin stabilization requires a rate of rotation so high that it becomes impractical to achieve this design constraint led to the development of the first armor-piercing fin stabilized discarding saba rounds because apfsds rounds are as the name suggests aerodynamically stabilized by fins they do not require the spin stabilization provided by rifling more than that rotation at the rate imparted by a typical rifled barrel will actually significantly reduce the effectiveness of these rounds apfsds rounds like apds rounds before them are pure kinetic penetrators that is to say they rely upon their kinetic energy determined mostly by their velocity to penetrate armor in the case of apf-sds projectiles rifling reduces velocity in two ways first because a portion of the forward velocity the type that matters for kinetic penetrator is converted to rotation while traveling down the barrel but second and more importantly after exiting the barrel the rotation of the fins causes them to whip through the air massively increasing drag this will further reduce the velocity of the projectile at any range but the effect worsens the further away a target is greatly reducing the penetrative ability of apf-sds projectiles at medium to long range to counteract this effect somewhat attempts have been made to reduce the degree to which rifling imparts rotation to these projectiles with varying degrees of success while a small amount of spin actually does benefit thin stabilized projectiles this is typically achieved simply by canting the fins at a very slight angle relative to the penetrator and even in the case of apfsds rounds that are specifically designed to be fired from rifled guns the rate of spin is still significantly higher than optimal resulting in noticeably reduced performance the true solution for either apf sds or heat rounds is simple remove the rifling from the gun this is exactly what soviet designers did with the t-62 the first tank to use a smoothbore gun the soviets understood that the primary job of a main battle tank is to destroy enemy armor principally the enemy's own main battle tanks they also understood that the next generation of western tanks which they expected to fight would include thicker and more advanced armors that would necessitate the use of advanced ammunition such as heat and early iterations of apfs dias rounds in order to defeat them it took western countries another generation of tanks to follow suit in part because the soviets did not have comparable advanced composite armor until later in the cold war however in 1979 the german leopard 2 became the first western tank to use the rhyme metal rh 120 millimeter smoothbore gun which began development 14 years earlier in 1965. in the following years all of the new third generation main battle tanks would eventually switch to using smoothbore guns all of them except for the british challenger 2. that brings us back to this image from the thumbnail but this time instead of asking why do modern tanks use smoothbore guns we can ask two better questions why is the british challenger 2 the only modern tank that doesn't use a smoothbore gun and more specifically why is the british military planning to change the gun on the upgraded challenger 3 now however the answers to both those questions will have to wait for a future video if you enjoyed this video and want to see more please consider hitting the like button and subscribing to my channel defuse some ideas this is my first youtube video and i'd like to thank anyone who's watched at this point for your time and attention i plan to produce more content like this covering a wide range of topics and varying from purely fact-based to expressions of opinion as well as releasing a series of less highly produced vlogs and interviews to fill in the gaps i'd love to know your thoughts on this video and get ideas for future videos also after watching this do you think that rifle barrels are gone from tanks for good or could they make a comeback let me know in the comments below

Channel: Diffusum Ideas

Views: 651,874

Keywords: Tank, Rifled, Smoothbore, APFSDS, HEAT, Anti-armor, gun, canon, Sabot, Russian, American, British, German, Anti-tank

Id: EzkPkjEHD5g

Length: 8min 59sec (539 seconds)

Published: Mon Apr 11 2022