I just completed a AR-15 accuracy build and now find myself trying to decide on a scope.  I plan on shooting from 100 to 300 yards routinely and up to 500 to 600 yards on occasion.  Because of this, I feel that a first focal plane scope would be my best option.  Is there any reason to pick a second focal plane over a first focal plane? Second, I need to decide on a magnification range.  After doing a little research on this forum and a couple of others, I see that you will get recommendations for upper magnification of anywhere from 10x up to 25x or so.  Is there really anyway to calculate the upper magnification needed at a certain range?  For instance, if I split the range of 10x and 25x, I come to around 18x or so.  I see that Meoptic makes a Optika6 3-18x50 that is available in a FFP.  I have never personally owned a Meoptic scope and haved looked through them only on a couple of occasions at best.  Would this scope be something that I should consider for my build?  I understand that Meoptic scopes are generally considered very good, but does anyone know if the Optika6 lives up to the reputation of the previous models?  I only ask this because of the common opinion that the Terra line doesn't live up to Zeiss's reputation.  I see that Meoptic also makes a 4.5x27 scope in the same Optika6 line, will this fit my needs or is it too much magnification?  Beside Meoptic, is there any other brands of scopes and/or magnification ranges that I should consider?  Burris Verocity and/or XTRII?  Vortex?  Bushnell?

I'd look pretty hard at the new Nightforce NX8 F1's.  You can get a 2.5-20x50 or a 4-32x50.  For the type of shooting you're describing, the 2.5-20x would be fantastic.

That is more mag and glass than needed for 600.  40mm and 10X works just fine.

OP, slap a lower end Vortex on it and find out of it is worthy of expensive glass.  It might not be worthy.

There's no need to handicap yourself right outta the gate.  2.5x is pretty low on the power scale, shouldn't be overkill at all.

More glass than needed? Sure, but 20x isn't going to be too much at 600. After shooting at 1k with a 3-9 I'm looking at that exact 2.5-20.

Eotech Vudu is perfect for that type of build. It is what is on my AR10 for similar idea. Great Scope and can be had on here or ebay for a decent price..