Thread: Focal plane, first and second

This is very new to me, focal planes so I'd like some advice please.
I bought a vortex diamondback 4-12x40 scope with dead hold bdc for my 223. I have sighed it in, chronied my ammo and input the data into strelok app.
It tells me that the second mark down is 187m for that info at full magnification.
My question is, with it being second focal plane the bdc reticle doesn't enlarge so does that mean the range for the bdc marks stay the same on all zooms or does it does it change as you zoom because the target enlarged?

I was looking into buying the strelok+ app to get more options including the ranges at different zooms but from what I have been reading I may not need to.

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