Understanding Tanks

[Penguin]

Smoothbore canons have exactyl that a smooth bore. They can achieve somewhat higher velocities than a rifled gun, but are less accurate. Rifled gun have rifling on the inside of the barrel called the bore. This rifling imparts a spin to the round as it is pushed down the bore by the expanding exhaust gasses of the propellant. This spin makes the weapon more accurate. The longest tank on tank kill was achieved by the British using a rifled L11A5 120mm gun. The longest tank vs target hit of all time was General Tal of the IDF's hit on a Syrian bulldozer at something like 6km using a rifled L7/M68 105mm gun.

However:

To reliably penetrate the thick armor of modern armored vehicles, a very long, thin kinetic-energy projectile is required. The longer the projectile is in relation to its diameter, the higher the spin rate must be to provide stability. Practical rifling can only stabilize projectiles of a limited length-to-diameter ratio, and these modern rounds are just too long. These rounds are instead formed into a dart shape, using fins for stabilization (see kinetic energy penetrator for information on how this works). With the fins for stability, rifling is no longer needed and in fact the spin imparted by rifling would degrade the accuracy of a finned projectile.

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