Re: ffp mildot question
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Remoah</div><div class="ubbcode-body">imagine you are looking at a picture on a piece of paper.
and then you draw the Mil Dot reticule over that picture with a marker.
Thats what an FFP scope is like, the image of the crosshairs remains 'overlaid' on the image.
Depending on the zoom level, your point of impact WILL NOT change, just as occurs in a second focal plane scope.
The reason behind FFP is that if you sight your scope in so the crosshairs are accurate at 300m, the second dot is accurate at 400, the third dot at 500 and so on, if you zoom out to 6x for a shot at 300, and then zoom in to 10x for a shot at 500, the point of impact on the dots will not change, as the reticule size has not changed, just the amount of zoom.
EDIT.
So YES, you are correct. </div></div>
Fail. On many levels.
This is an example, not exact, but this is for the 168 grain OTM leaving the muzzle at 2600 fps with a 300 yard zero. Caclulations provided by JBM ballstics.
You can see that indeed the drop at 400 yards is 1 mil. That is the ONLY time that this happens, at 500 yards you are off by .2 mil, not terrible provided your estimation was good, at 600 yards you would be off by 1/2 mil and it only gets worse from there.
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (mil) (mil) (mil) (mil) (ft/s) (none) (ft•lbs) (s) (mil) (mil)
300 -0.0 -0.0 0.2 0.2 2042.8 1.830 1556.5 0.390 1.9 1.9
400 -1.0 -1.0 0.3 0.3 1872.2 1.677 1307.3 0.544 2.0 2.0
500 -2.2 -2.2 0.4 0.4 1711.2 1.533 1092.2 0.711 2.1 2.1
600 -3.5 -3.5 0.5 0.5 1561.4 1.399 909.3 0.895 2.2 2.2
700 -5.0 -5.0 0.6 0.6 1424.5 1.276 756.8 1.096 2.3 2.3
800 -6.7 -6.7 0.7 0.7 1302.7 1.167 633.0 1.316 2.4 2.4
900 -8.7 -8.7 0.8 0.8 1198.8 1.074 536.0 1.557 2.5 2.5
1000 -11.0 -11.0 1.0 1.0 1114.8 0.999 463.6 1.817 2.7 2.7
That does not mean you can't use the mil-dots for hold overs, but you don't just sight in a 300 and use each dot as a holdover at every 100 yard increment.
With a FFP scope, the relationship bwtween the target and the crosshairs remains constant. You can mil at any power, you can use your mil-dots for holdovers and leads at any power. That does NOT mean that you just use the next one in line for every 100 yards.
With ANY good quality scope, SFP or FFP, your point of impact will not change when you adjust the adjust the magnification.
With a SFP scope, the mil-dots are only accurate at one setting, that does not mean you can't use them at different settings, it just means you have to "map" them at those different settings.