Re: FFP and SFP and ranging
I've been a fan of FFP for many years, however; they are just catching on here in the US in high quality optics. Only downside I've seen in some FFP scopes is that sometimes the subtension (reticle thickness if you will) is not as fine as I'd like it to be.
Yes, you answered your own question. 2nd FP optics Have to be on a particular power for the reticle to work as advertised. Sure, you can change the magnification, and still use it as needed. We just have to realize that the spacing will change as we change power, and calculate how much.
In my case, a 1/2 mil mark/dot at 25X changes to 3 IPHY at 15X......less power = more spacing.
(25/15=1.667...........1.667 X 1.8 IPHY (1/2 mil) = 3 IPHY)
If I want the spacing to be 2 IPHY (basically 2 moa), then the scope needs to be on 22.5X
(1.8x = 2, so x=1.111...........25/y = 1.111, so y=22.5 power)
This of course is in algabraic theory, and obviously should be verified at range on an actual grid; because not all scopes magnifications and zooms are exactly as advertised.......It does work out very well on the particular scope I have.
Last edited by SBruce; 01-03-2011 at 04:10 PM.