I recently built myself an AR10 with a match grade barrel and all the trimmings which I am planning on using for some long range shooting. I will eventually take a class and I do know how to calculate drop and use my scope for long distance but I dont know about Spin drift and when to compensate for it in my calculation of MOA for a shot. At what distance do I need to start adding an extra MOA or half MOA? and When I see mirage on a long distance shot. is there a typical distance mirage appears? is there a best distance to read mirage for calculating wind if I dont have any flags between the target and I? I probably need to do some reading or take a class but for now I figured I would get peoples opinions here. I have never seen a forum of such professionals. Its nice to be a part of this, even If I dont have a lot to contribute. thanks for any and all help you can give. also I would post a pic of my rifle but I dont know how....