I'm building a 6 ARC AR15 with an 18" proof carbon fiber barrel. I'm into long range shooting, so I will take advantage of the 1100 yard supersonic range of the round (and potentially try to push it much further if I can find a range with that opportunity). I'm trying to decide between the 2.5-20 and the 4-32 NX8 as primary optic. I'll also run an offset RDS for close in shots. I like my rifles lightweight, so I shave weight where it makes sense to (like dropping a pound with the CF barrel). I'll be running a PRS lite stock. The 4-32 is only 1oz heavier and about $100 more. Which way should I go? What's the minimum practical usable magnification on the 4-32? If it's worthless under 8x for example, I'd go with the 2.5-20. But if 5 or 6x is usable, I'd prefer to have the higher end available for spotting my own impacts when mirage and weather allow cranking it up above 20x.