Rifle Scopes Mill Dots 2nd Focal Plane Variable Power Scope

[tikka6.5]

On a 2nd focal plane scope with variable power and mil dots, how do you know where point of impact is going to be at different powers?
I have just been leaving the scope on the same power and using the mil dots to hit different steel gongs at different yardages. I dont have a range finder so I dont know the distances are.
Is there a formula or do you just have to do shooting at each power and make notes?

 

[ShtrRdy]

The easiest approach to using a SFP scope with a ranging reticle is set the power ring on the correct power setting to make the reticle read properly.

It is theoretically possible to use a different magnification and calculate the readings of the reticle but that approach is filled with several possible errors.

 

[remr5]

magpul precision rifle video covers this in detail

 

[dAyLiTe]

If you're lucky, you scope is calibrated at 10x... then it's 'easier'.

Generally, you're looking at: 1 SFPMil = 1 Mil x ( Calibrated Magnification / Current Magnification ). Where Calibrated Magnification is the magnification at which 1 Reticle Mil is actually 1 Mil.

So if you have a SFP scope calibrated at 1 Mil when at 10x, then when you're at 6x, the Reticle Mil is actually = 1 Mil x (10 / 6) = 1 Mil * 1.6666 = 1.66666 Mil.
...and that's before you even start thinking of working out the range and point of impact. If you're working backwards, it's even 'more' fun... not.

Honestly, if you're getting into working out these calculations and are interested in reticle/turret units of measure, just go get an FFP scope... It'll mean more shooting and less math.... unless of course you love math more than shooting.

 

[roggom]

If you are shooting 8" gongs, you should be able to hit it anywhere up to MPBR, which is around 250Y with a 308, past that you have your scope set to x10, or dial for elevation. I do agree that FFP takes out all the frustration and you can find a used MK4 or new Weaver for approx $800.

To the credit of the SFP, with enough range time you will be comfortable with your rifle and will know where to put those crosshairs.

If you need another mag (lower) , then pic up some of Franks Training targets, and adjust your mag ring until one mil covers two mils on the target, then you know your holds will be double and range will be half. Only issue is there is much more room for error.

Example, I have a NF 2.5-10 @x10 there is a sign at 400Y. I use this same sign to verify my scopes, so the sign takes up a mil and a mildot = 1.25 mil the sign is 18" (i measured it) 18 x 27.77 = 499.8 then divide by 1.25 = 399.88 Thats damn close.

The issue is trying to read at the lower mag. Is the sign .5mil, .6 mil ? There is no frickin way to measure .625 mil as the sign is so tiny. using .5 mil will give 1000Y then divide by half = 500Y(off by 100y), using .6 will give 833Y, half is 416 which is not so bad, but not as accurate as when the ring is at 1:1 mag




Sniper's Hide Training Target (mil)