Those kinds of velocities and 'practical' are a bit of a contrast, don't you think? You're talking about pushing a bullet three to four times faster than modern, conventional rifle rounds are comfortably loaded for.
At those velocities you have to deal with the fact that air friction will literally melt the bullet, and worry about the bullet bursting into little shards inside the barrel; both of these problems have limited the development of magnetically and electrically propelled projectile weapons.
The M1A1 Abrahms tank's main gun fires a DU sabot round at about 5,000 FPS, pretty close to "the velocity limit for chemical propellants", per Wikipedia.
Is it possible? Sure, anything's possible. Not with a stock rifle or with components you can buy off MidwayUSA. Probably not possible with chemical propulsion (barring rockets
). But sure, you could theoretically make a gun that pushes a bullet that fast, if you're willing to stretch the definitions of 'rifle' far enough.
No, you don't want a bullet travelling that fast to hit anything you might want to take home. Even a very small projectile at that velocity would make a terrible mess out of anything it hit. Think 'fine red mist' or 'bloody, ragged pelt hanging from the trees' rather than 'small entry, big exit'.
Feasibly, anything over the current magnum velocities of 3,000+ FPS is pretty much overkill (I would argue that even current magnum loads are overkill, YMMV). There's a limit to how much energy you want to be pumping into a game animal via bullet, and typically you upgrade the weight/diameter class of the bullet rather than its velocity if you're hunting bigger, more dangerous game.
