Posted: Mon Jul 21, 2014 11:33 am
Just a word of warning - not all crosshairs are perpendicular/parallel to the axis of scope travel. One big brand was infamous for having slanted crosshairs a few years back.
Whether you use a plumb bob, spirit level on crosshair, spirit level under base or spirit level across turrets - all should be checked when you get a new scope by a simple procedure at a short range zero.
e.g. 25m range (ensure parallax error is minimal - very hard at short range and bubble is level) and fire some shots setting your wind zero at a 300 or 25m zero. Then wind up to 900 or 1000 yard settings (or over 20 minutes) and fire a few more. Check the impact point with a level or plumb line - they should be vertical - remember at 25m 7.3mm = 1 minute.
It can be done further out but wind must be taken into account.
Alternatively if you can clamp your rifle or scope in a solid device you can just wind and watch crosshair rises vertically. up a plumb/vertical line.
Whether you use a plumb bob, spirit level on crosshair, spirit level under base or spirit level across turrets - all should be checked when you get a new scope by a simple procedure at a short range zero.
e.g. 25m range (ensure parallax error is minimal - very hard at short range and bubble is level) and fire some shots setting your wind zero at a 300 or 25m zero. Then wind up to 900 or 1000 yard settings (or over 20 minutes) and fire a few more. Check the impact point with a level or plumb line - they should be vertical - remember at 25m 7.3mm = 1 minute.
It can be done further out but wind must be taken into account.
Alternatively if you can clamp your rifle or scope in a solid device you can just wind and watch crosshair rises vertically. up a plumb/vertical line.