A Russian inventor emailed me photos of his patent-pending bullet design. These bullets are loaded in 12.7×108mm cases.
The inventor did not explain to me how this design is beneficial but according to a study done by the US Military in the 1950s (PDF Link), the center of gravity affects how a bullets will yaw when it encounters a solid object. Yawing (and tumbling) can be reduced by make a bullet nose heavy.
Not long after that report was published both the USA and Russia adopted cartridges designed to tumble upon hitting the target. The 5.45×39mm round actually contains a hollow cavity in the nose to make it base heavy.
The benefits of tumbling bullets on soft targets is still hotly debated but for anti-material and anti-armour applications penetration is the name of the game.