The gun you have is a good gun, so don't give up on it yet. I got mine calibrated the first time using it, but after messing with the cabinet I needed to calibrate again. I know how frustrating it can be, but make sure there aren't any other "signals" that will interfere with it and make sure your drivers are up to date.
Try calibrating at different distances and at different points on the screen. Once it's calibrated, you shouldn't have to do it again and you can enjoy it.
I know that didn't answer your question, but I thought I would throw in my .02