Re: M 1 turret
Like most 'standard' turrets, the M1 depending on your model is a 1/4 MOA click adjustment with 90 MOA total for windage and elevation adjustment. At a mechanical zero you should have 45 MOA in either direction.
The set screws on the turret allow you to dial in your zero then set your '0' position on the turret to coincide with the markings on the scope body by loosening the set screws, moving the turret to its desired location and then tightening the set screws to fix the turret to its new position.