Animation Rotation problems ( animating a rotating turret)

im trying to animate a turret from a game that I pulled the model from.

now the problem Im having is the rotation of the pipe section. I can rotate and keyframe enough time times to create a complete rotation, but when i dup those keys so I can do the rotation many times, it reverses itself. can someone help me? or perhaps show me a way to rotate the turret without so much keyframing? here’s the newest .blend from 2.37 that I created, I was keyframing in the nla.

enter 2 keyframes
in the IPO window (Shift F6) select the Curve>extended mode>Extrapolation