Just as a check on the hand spring, take off the sideplate. You may also have to remove the safety bar. Push the hand forward toward the cylinder and pull the trigger to cycle the action. If the hand engages and rotates the cylinder, then the torsion spring or torsion bar, depending on what design you have, may be the problem. Those parts are inside the trigger assembly so the trigger will need to be removed to work on them. Sometimes on the older guns with a torsion bar and coil spring, the spring loses engagement with the forward end of the bar. Over time, it may also become distorted or bent. Just remove it from inside the trigger and straighten it. You may have to stretch it slightly to straighten and restore tension. Don't pull from the ends. Instead, roll the spring on a flat surface while pressing it with your finger tips along the whole length. It only has to stretch slightly to restore tension. If it is broken, try ebay for a spring from a Victory revolver.
If you have the new pigtail-type torsion spring, it is likely broken. You should be able to get a replacement from Brownell's or MidwayUSA.
