Depends a lot on what you're shooting at 300-600 yards away. Paper, steel, one of God's creatures, something that shoots back?
For paper at 600 the 14X won't be enough. 6.5-20 or 8.5-25 would be a little better and even more power, like 36X-40X better yet.
Live critters? Groundhogs, prairie dogs, etc. 12X is really not enough power at 600. Even a big old woodchuck looks mighty small at that range.
24" steel gong. Would probably work. Big old target.
Also, "how clear is it" doesn't really matter. That scope is at least 8 years old but if there is a problem Leupold will fix it.
It's rather foolish to recommend a specific scope, especially a FFP, when we don't know what the target is.
Nice jab, Dave. Obviously if the OP is considering buying that 4-12 he's not looking to win any BR comps, or apparently doing anything other than casual shooting or hunting.
So let me get this straight, are you saying that a FFP scope isn't capable of being used successfully for other shooting disciplines besides tactical and field course, like BR, F-class, ELR or how about hunting too? I guess I better sell my S&B 5-25's and March FX 5-40 then, lol.
I don't shoot BR BTW but yuh know, that was just foolish of me to use my FFP S&B to win the only ELR match I've shot in and to hit the farthest target also, a 2356Y plate.
Or being foolish enough to use a FFP scope to get high score by 4 points in the 2016 AZ state FT air rifle, and 2017 winner in Freestyle division.
Or being 2011 and 2012 AZPRC champion with a FFP.
Uh, this is why I suggested a versatile FFP scope to begin with. Is it ideal for 600Y paper, maybe not, but consider this, the crosshair covers only .54" at 600Y and 14x could be considered an upgrade over 12x.
More education...
With a FFP scope objects of known size can be ranged for approx distance at any magnification via the reticle and a math formula.
The reticle sub-tension values remain constant on any magnification, this includes the reticle hash thickness.
Therefore one can adjust magnification and FOV to suit the situation and use the hashes for holding over, and off for wind, with the reticle. Or dial the solution and hold for wind, or dial both elevation and windage. Heck you could even dial windage and hold over if you wanted to.
Now that we have more information, suggestions can be narrowed.
So Blue, what is your max budget?