During the Desert Storm tank shootin' match, there was one British Chieftan I tank gunner who managed a hit with a Chieftain's 120mm main gun with a SABOT round that hit one Iraqi T-72 nose-on, went all the way through the front slope armor, turret basket area [tho T721 doesn't have a basket per se] then on through the engine pack and out the rear armor...to hit a T-55 parked sideways behind the T72, which the round continued through, in one side and out the other. The Brits got their money's worth from that round.
Most of the American and French tankers who'd seen the results from their 105mm main guns were quite happy with them, but those who'd seen what the 120 could do were really impressed, with many wishing we had something along the same lines. And now we have!
But that is a wee bit bigger than the 5.56mm M855 NATO ball round.
And a bit heavier. It takes a pretty good-sized feller to horse around the 100/105/120mm main gun rounds of a tank, and a lot of armor units spend descretionary unit funds on dayroom weightlifting equipment, which pays off when it's Table 8- tank gunnery for score time.
