don't come crying to me when your bullets go up so much they do a full loopdeloop and shoot you in the back of your head because you tried to fire them on the moon where there's no gravity
But actually, if you had no gravity acting to change the velocity vector, the bullet would continue in a straight line. If you shot at the horizon it would be like drawing a straight line tangent to a circle. The bullet's not going to end up going in the shooters azimuthal direction, but it sure is going to gain altitude as the curvature of the body peels down way away from the straight line it's flying,