Finally, a topic on which I can lend useful information...
Buckeye Mike has it right. To be more specific, when you hit a golf ball, the intent is to give some backspin, producing lift. That will happen whether or not there are dimples on the ball (based on Bernoulli's Principle), but the dimples 'catch' the air and create the necessary resistance to improve the effects of that spin. Sometimes, the spin is lateral, causing slices or hooks, or top-spin resulting in a 'worm-burner'.

The same principle works on a round ball bullet, but you are not likely to see much effect if the bullet is dimpled. The reason is the shape of the arc travelled by the bullets. Golf balls move in a fairly slow, high arc. Bullets move in a fast, shallow arc. Also, when the galf ball takes off, it is starting at the bottom of the arc, travelling to the top, then falling back...it travels the full length of the parabola.

A bullet starts out closer to the top of the arc, and eventually falls to the ground. The bullet does not get the benefit of the dimple-enhanced lift on the way up the curve. Add to that the fact that a barrel's rifling causes spin only on one axis, perpendicular to the path, and there is little or no added effect.

Now, if you were to shoot round balls out of a smooth barrel, aiming at 45 degrees, I bet you'd see some difference in the distance travelled between dimpled and smooth balls. You'd be using the full length of the curve and not introducing z-axis spin.

Cheers
Rob