One of "Murphy's Laws of Combat" is that "The best tank killer is another tank. Therefore tanks are always fighting each other ... and have no time to help the infantry." One of the reasons this rings true is because the rounds used by tanks to kill tanks are so darn effective. The sabot round that became known as the "Silver Bullet" from American tanks is the M829A1 for the M256 main gun on the M1A1/M1A2 Abrams main battle tanks used by the Army and Marine Corps (plus the Saudis, Egyptians, Moroccans, Australians, Kuwaitis, and Iraqis). This round uses a hardened dart dubbed a "sabot" to punch through an enemy tank. And the M829A1 did a lot of that in Desert Storm.
The M829A1 is an armor-piercing fin-stabilized discarding sabot – APFSDS – round. The long-rod penetrator is usually no more than 1.25 inches wide and is held in a "shoe" that enables it to be fired in a gun whose bore is a little under five inches long. When the round is fired and exits the barrel, the shoe flies off, and the round is on its way.
The long-rod penetrator then flies downrange towards the target. Once it hits, the round just punches through the armor. The result is the enemy tank tends to blow up in what tankers call a "Jack in the box."
How well does it work? Well, in Tom Clancy's "Armored Cav," the stories abound. One "silver bullet" killed two T-72s with one shot. Another, fired from an Abrams tank that was stuck in the mud, penetrated a sand berm before it blew up a T-72.
That was the M829A1. Since 1991, the United States has switched to the M829A2, which made improvements to the depleted uranium penetrator. Globalsecurity.org notes that the M829A2 round was late replaced by the M829A4, which has even further improvements to the penetrator and adds changes to the sabot.
Check out the video below to see what the sabot round does so lethally well.