What would be the effect of a slant barrel on the trajectory of a bullet?

Let's say I saw the barrel of a gun with a 45° angle, what would be the effect on the trajectory of a bullet fired through that barrel ?

Would the bullet be less stable (I guess), would it make the gun fire with an angle, and would that be toward the "small" end ?

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Is this related to muzzle brakes? –  dmckee Mar 2 '13 at 20:32
@dmckee well, I didn't know about that, but if you formulate an answer mentioning the fact that it's the principle of muzzle brakes, I'd accept it. –  Zonko Mar 4 '13 at 15:23