The M1028 is a 120mm shotgun shell for the M1 tank. The shell holds 1100 10mm tungsten balls. They are apparently lethal up to 700m (765 yards). Here is a video of the shell being fired in slow motion. It shows the shot breaking the sound barrier and the shot pattern (H/T to Sebastian).

I tried to calculate the weight of each ball. It depends on how pure the balls are. My calculations, based on a company that makes tungsten balls that weigh 18 grams per cm3, indicate that each ball will weigh about 145 grains. That is a combined weight of 159,500 grains / 10 kilograms / 22.8 pounds!

(4/3) x pie x 0.5cm ^ 3 = 0.52 cm3
0.52 * 18 = 9.42 grams (145 grains)

Please correct me if I am wrong.

The requirements of the round were:

• Defeat >50% Advancing Squad w/ 1 Shot
• Defeat >50% Advancing Platoon w/ 2 Shots
• 200-500M (threshold)/100-700M (objective)
• Muzzle Action (i.e. No Fuze)
• No orientation of the projectile
• Vulnerability no worse than current fielded

The M1028 cross section.

Here is a before and after shot taking during the testing of the round. I am not sure of the range.

Before

Two dummies survived, the wall did not.

The concept of shot is not new. Grape shot or loose stones, metal and glass have been used for as long as cannons have.

American Revolution grapeshot

Sources of information:

M1028 – GARM Final (PDF)
Military.com
PSMVCC (PDF)
JinJu Powder Metallurgy