Why tungsten? Weren't Claymore ball-bearings steel?
I seem to recall the Germans had a good anti-tank gun that
fired a sabot-tungsten round, but that was to pierce metal.
Tungsten is more dense than steel, holding energy more efficiently at longer ranges.
Speculation: Better penetration of light cover. This round will probably shred thin-skinned vehicles, walls, trees, thin berms, etc.
Not to mention shredding BGs.
Tungsten is much denser than steel and retains more kinetic energy over distance, so it penetrates better at longer ranges. This is especially important with a round ball since they have poor sectional density (ratio of diameter to weight).
Tungsten is more dense than regular steel.
This means that the balls will lose less velocity over longer ranges than lighter balls of the same diameter. The hardness helps a little, but not as much as it does on the penetrator rods.
Recently, there's been experiments with tungsten core bullets for the M-16/M-4 series rifles. 82+gr, IIRC, which can be loaded in magazine length cartridges. Holds more velocity over longer ranges, as well (not to be confused with the Black Hills 77gr loads). Very expensive and there's some experimentation with powdered (sintered) metal construction. It's very difficult (impossible) to melt tungsten into a copper jacket and you can't economically machine the bullet cores.