Bushnell legend

[GPConway]

All it means in practical terms is Chairgun type dot range zero's (holdover) will be out because their maths is at 10x true. but their 10x holdover will be your 15x their 5x your 7.5x their 6.6x your 10x, their 3.3x your 5x etc (if you follow)

ChairGun's 'maths' is based on whatever you say the calibration magnification is.
Use the Reticle Calibration applet - or do the sums manually if you're that way inclined - and the conjecture ends in ten minutes flat.

George

[angrybear]

Thanks George never spotted that it can be changed from the pre-set "true" must look.

OK, I've looked but can't see how ??

[GPConway]

Thanks George never spotted that it can be changed from the pre-set "true" must look.

OK, I've looked but can't see how ??

Since the Bushnell Legend isn't a Hawke scope, choose the 'Generic Mil-dot' reticle.
If you're using the latest version (V4.3.1 I think) then the calibration mag of any reticle is adjustable via the Reticle Calibration applet (Toolbox >> Calculate & Calibrate >> Reticle Calibration ... or by right-clicking on the Cal.Mag textbox and selecting the Reticle Calibration item from the popup).
If you're using an earlier Chairgun version then, once the Generic Mil-dot reticle has been selected, you can select the 'Calibrate Generic Mil-dot' (or something like that) option from the Toolbox menu.
The two applets aren't identical but they both do the same thing.
In either case, there are details in the appropriate helpfile.

I don't know why you would want to but you can do the same calculation by hand from:

C = M * T * 100 / (R * 3.6 * D)
where:
C = Calibration Magnification
M = Indicated Magnification (on scope)
R = range from scope-turrets to target (Yards)
T = Target Size (Inches)
D = Number of dot-spaces to span the Target

or, in froggy units:

C = M * T * 100 / (R * 10 * D) = M * T * 10 /(D * R)
where:
C = Calibration Magnification
M = Indicated Magnification (on scope)
R = range from scope-turrets to target (Metre)
T = Target Size (cm)
D = Number of dot-spaces to span the Target

For example:
I once had a cheapo Chinese 3-9x Mil-dot scope allegedly calibrated at 10x but disparity with Chairgun's predicted aim-points indicated that it was nowhere near. Twiddling the calibration mag in Chairgun until the predictions and reality matched, it looked more like 12x.
I found a scrap of wood, scribed two horizontal lines on it 12" apart and, with the scope set to 9x, walked towards the wooden target until the two lines were spanned by 10 full mil-dots. That happened at around 76 Feet (25.3 yards) from scope-turrets to target and measured with a surveyor's tape.
So:
C = M * T * 100 / (R * 3.6 * D) = 9 * 12 * 100 /(25.3 * 3.6 * 10) = 10800 / 910.8 = ~11.9x

George

[angrybear]

Thanks, I'd found the bit in toolbox but no explanation as to how to use it, now found the details towards the bottom of the help file.