Question on tank guns

[billytran 0]

On a tank's main gun, the bore is either rifled or smooth. The original M1 Abrams tank had a smaller, rifled bore. The M1A1/A2 have larger smoothbore guns. I know that rifling makes the round spin, thus increasing range. So, I'm guessing that the advantage of smoothbore guns is a greater punch, am I correct?

[Guest]

Rifling makes the round spin which stabilizes the round (i.e better accuracy, shorter range since a part of the kinetic energy is used to spin the round)

Smoothbore = greater range = greater punch

[RedRogue 0]

However if I remeber correctly the fins on the APFSDS (<<correct acronym?) are angled to spin the sabot in the air. So you get the gyrostabilization of rotation without the resistance of rifling. Plus smoothbores are much easier to clean and less prone to loading issues caused by rifling.

[Mister Frag 0]

Modern tank guns have smoothbore barrels because they use Sabot projectiles, which are drag-stabilized, and not spin-stabilized.

The actual kinetic penetrator is enclosed in a bore-sized carrier (the sabot, 'sabot' = french for 'boot' that falls away after the sabot leaves the barrel. The penetrator is very much like an oversized dart.

[USSoldier11B 0]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">However if I remeber correctly the fins on the APFSDS (<<correct acronym?) <span id='postcolor'>

Yes this is correct. APFSDS stands for Armor Piercing Fin Stabilized Discarding Sabot. Denoir is correct, a smoothbore drag stabilized round packs more punch. The dartlike submunition is construction of super dense alloys such as tungsten steel or depleted uranium. The penetrator achieves a very high velocity and has a high length to width ratio. The technology is purely KE, it is a battle between armor thickness and penetrator decay. As the penetrator pushes through the armor it becomes shorter until it either bursts through the hull spalling the crew members with pyrotic fragments or comes harmlessly to rest in the center of the crater. Generally, the greater the length, the more effective the round is up until the point where velocity becomes compromised by drag and weight. Developers strive to make penetrators with high length to width ratios up until the point where the penetrator becomes too thin and could possibly bend upon impact. Initial rounds had ratios of about 1:9, nowdays the can range up to 1:28 or even more.

"The US Army tank crews nicknamed their depleted uranium M829A1 Armor Piercing, Fin Stabilized, Discarding Sabot-Tracer (APFSDS-T) the 'Silver Bullet'. The hyper-velocity M829A1 round allowed M1A1 Abrams crews engaged targets at very long ranges. The penetration characteristics of tank gun APFSDS darts was so great that enemy tanks could be engaged behind sand berms, the sub-projectile penetrating between ten to thirty meters or sand and still achieving a hard kill. It has been reported that a single M829 round pentrated and destroyed two Iraqi T-72. Apparently they happened to be in line, the 'silver bullet' simply punching through the first tank to hit the second."

Defense Industries - U.S. Army