I recently acquired a Comp M2, and I need to set this back to a factory zero. This is WELL out of zero for me-I havent had the opportunity to shoot it yet, and likely wont until mid Jan. I want to get it to factory zero though, to minimize fudging around with it when the time comes to zero it. As this little device is sort of a new toy to me, I am not sure if I simply center it by eye, or if there is an actual zero. Any advice would be appreciated. Thanks.