1st plane and 2nd plane

[brnzbk]

Hi again
I have been looking at scopes for my AR 15 build and i have a question, how accurate will a bullet drop, mil dot, reticle be if it is in the 2nd plane of focus. I've seen many ads for these but I am skeptical. If I understand this correctly if the article is in the 1st plane of focus it will appear proportional to the target through the zoom range. Conversely if the article is in the 2nd plane of focus it will appear the same size throughout the zoom range, thus looking much larger on the target at a higher magnification than a lower one. So how does one use these tools to estimate range when zooming in on a target when the article is in the 2nd plane of focus, am I missing something?
Thanks for your help

[Bwild97]

Ranging or Mil-dot reticles that are set in the second focal plane are only accurate at 1 or 2 specific magnifications, like a Millett LRS-1 6-25x56mm. The mil dot bar is accurate at 12.5x and 25x with .1 mil clicks

[Drifter]

Bwild is correct. Second focal plane makes the reference points of the reticle applicable only at a particular magnification (usually at max power, but can vary by model).

First focal plane means that the reticle maintains the same relationship to the target throughout the power range, thus making the reference points usable regardless of power setting. This can become increasingly important in hunting applications, where as magnification is often reduced for a larger exit pupil (better perceivable light transmission) during low light conditions, at which time dialing up for a long shot can be a challenge. With FFP, both range estimation and holdovers are still applicable regardless of what magnification the scope is set on.

Also, there should be no POI shift when changing power on FFP scopes, where as POI shift is reportedly nearly impossible to avoid with SFP. Of course, top-quality SFP scopes will exhibit minimal POI shift.

I consider FFP scopes to be superior for my application. But a couple of downsides include a small difficult-to-pick-out reticle at the lowest power settings, and they are more costly to produce (thus carry a higher price tag).

[stokesrj]

It really is a matter of personal preference with gives and takes on both sides. The reticle in the second focal plane is by far the most common set up and the one that I prefer. The drawback is that you must have it on the highest magnification or multiples of to use the ranging function. The downside of a first focal plane reticle is that it appears very large at high magnification and very small at low magnification which is exactly the opposite of what you want. But you don't have to worry about the magnification being set to a specific power to use it for range finding.
What I have found to be most satisfactory for actual field use, and by that I mean hunting big game at extended range, is a moderate power scope and a reliable turret system customized to your load. My favorite is a custom version of the Leupold VX3, 30 mm tube 4.5-14X 50 mm objective. Here are a couple of links to this scope and a video of it in use in the field.
http://www.youtube.com/watch?v=_aNyJB60_6o
http://www.greybullprecision.com/index.p...ticle&id=5
http://www.greybullprecision.com/index.p...ticle&id=5