Many of these experimental designs also suffered from political infighting between factories and also from constant changes in Kremlin leadership. Upheaval continued as the nation ditched communism for capitalism.

“It is very difficult when designing advanced weapons to get a lot of money one year and see it taken away the next,” Zaloga notes. “There have been a whole string of [Soviet and Russian] next-generation tanks that failed.”

The Russian army is hoping to get brand-new T-15 tanks some time in 2015 as part of the Armata program. And Zaloga expects the new armored beast to be similar the relatively roomy American M-1 or German Leopard 2—in other words, a clean break from Soviet-era tank design, which emphasized small, hard-to-spot vehicles.

A larger overall layout could theoretically open the door for one of the legendary massive cannons to finally make an appearance on an actual front-line tank. But sheer practicality is more likely to compel Uralvagonzavod—Russia’s last tank factory—to use some sort of upgraded 125-millimeter weapon on the T-15.

And there are also firepower advantages to sticking with a more modest gun size. “The 120 caliber has continued to be a more powerful weapon,” Zaloga explains.

That’s due in part to intensive R&D on new cannon rounds. Having standardized their guns, the Russians—along with the Americans and the Germans—worked on improving their ammo. All three countries are working on even more lethal armor-piercing, fin-stabilized, discarding-sabot ammunition.

These APFSDS rounds launch massive darts of dense metal such as tungsten or depleted uranium. The penetrators rely more on speed and accuracy than sheer size.

A T-15 with an 125-millimeter cannon shooting faster-flying projectiles would probably be just as deadly as one with a much larger main gun. It doesn’t make sense to buy a gigantic new cannon if better ammo has as much destructive effect.

Still, the Western defense press and their sources insist on reporting “sightings” of tanks with huge main weapons—even outside of Russia. Reports in 2003 claimed the Chinese were working on one of their own.

Reports of a new Russian tank with a 152-millimeter gun surfaced again in 2008. And fearing the reports are true, the Pentagon is apparently still doing concept work on a new M-1 variant with a 140-millimeter gun the military hopes will match the terrifying new Russian weapon.

The Pentagon, NATO and others might not have to wait much longer to find out if there is any truth to their decades-old gun fears. Moscow hopes to parade its brand-new T-15 tank at next year’s May Day celebrations in Red Square.

The new tank probably won’t have a new gun. But maybe, finally, it will. “With the Russians, you can never say never,” Zaloga says.