Assuming you want to control the rotation, such as a gun on a tank turrett then you could use pulleys and a standard servo. I've seen this method used on model warships to move sets of guns through a larger angular swing than a standard servo. Simply place a large diameter wheel on the servo, and a small one on the item that you need to rotate. With some maths to work out ratios, you might be able to get the result you want without having to overdrive the servo.