ChristopherPerrien wrote: The L7 is the best tank gun that has ever been made. A shooting contest L7 vs L11 vs L44 or 55 would be an interesting competition.
The Royal Ordnance L7 was a good gun, but it's old. You can only milk a 1950s design for so long. The hole punching power, even with the depleted uranium projectiles, was no longer sufficient by the 1980s.
Someone at the Tank Net forum said that in 1988, the U.S. Marines did a live fire test against an export model of the Russian T-72 and all 105mm DU rounds failed to penetrate. The folks at Aberdeen PG must have known that the L7 (M68) gun, at least for MBTs, was near the end of its useful life in the 1970s. For that is why the army wanted the 120mm gun for the Abrams tank. They had to wait longer than expected to get it because Rheinmetall was delayed by technical problems.