09-19-2020, 08:09 PM
We,
You might be mistaking a shift in POI between guns with a shift in scope level. Once that scope is level in the mount, it is level for all rails. That said, if you take it off and on I have no doubt there will be a POI shift between guns, and even with the same gun.
To level a scope we do it on a rail. That rail needs to be level to the gound to avoid the gun being canted while levelling. So, we level the rail with a bubble and then level the scope somehow; using the base of the scope, or top of the turret, or eyeballing it, or using a downrange plumb line (best). Then test by shooting to make sure the plumbed reticle is square with the internal erector mechanism. To do this we Zero the gun. Then plumb a vertical line on a target: (1) fire a few rounds at the base of the line, then (2) dial it up 10Mils and fire again. Look to see whether the MPI of the two groups are in line with the vertical plumbed line.
Once you have done all this you know the scope is level with the rail. Taking it on and off any rail will be the same - the mount is now level with any rail it sits on. It doesn't matter if it is QD or screws, if you remove a scope from a gun while leaving it in the mount it will level for all guns. The POI shift you refer to is the vagaries of the permanent difference between the axis of a gun's rail and its barrel, made worse if there are different ambient conditions. In a good quality trued/blueprinted gun the barrel axis and its rail will be perfectly aligned, but they never are, especially when the barrel whips around while being fired. All guns are fdifferent in this respect and that's why you see the difference in MPI - and there's nothing you can do about it except re-zero.
You might be mistaking a shift in POI between guns with a shift in scope level. Once that scope is level in the mount, it is level for all rails. That said, if you take it off and on I have no doubt there will be a POI shift between guns, and even with the same gun.
To level a scope we do it on a rail. That rail needs to be level to the gound to avoid the gun being canted while levelling. So, we level the rail with a bubble and then level the scope somehow; using the base of the scope, or top of the turret, or eyeballing it, or using a downrange plumb line (best). Then test by shooting to make sure the plumbed reticle is square with the internal erector mechanism. To do this we Zero the gun. Then plumb a vertical line on a target: (1) fire a few rounds at the base of the line, then (2) dial it up 10Mils and fire again. Look to see whether the MPI of the two groups are in line with the vertical plumbed line.
Once you have done all this you know the scope is level with the rail. Taking it on and off any rail will be the same - the mount is now level with any rail it sits on. It doesn't matter if it is QD or screws, if you remove a scope from a gun while leaving it in the mount it will level for all guns. The POI shift you refer to is the vagaries of the permanent difference between the axis of a gun's rail and its barrel, made worse if there are different ambient conditions. In a good quality trued/blueprinted gun the barrel axis and its rail will be perfectly aligned, but they never are, especially when the barrel whips around while being fired. All guns are fdifferent in this respect and that's why you see the difference in MPI - and there's nothing you can do about it except re-zero.