The nx8 is a decent scope, I personally wish they'd stuck with 6x erector because anything above 24x is darkened, parallax constantly needs adjustment and DOF isnt the best. I have the 4-32x50 milC version. The glass for the most part is pretty good a step up from nxs but not atacr. I personally believe the mk5hd has the edge on glass rating and low light performance, but you're comparing a 5x erector vs an 8x. I swapped out my nx8 for the new Burris xtr3 3.3-18x50, and I loved everything about that scope, parallax and eyebox wer quite forgiving, glass is noticeably better than the NF. However after 30 round through a braked lightweight 300 norma improved, the reticle was shifting when I indexed the power ring between + -. This rifle is pushing 230s @ 3000 fps, there's a lot of punch there and with the brake, it's a recipe to kill optics. I just sent it back to Burris yesterday. Remarkably I put a nice whitetail down at 250y 5 rounds prior to me noticing the issue. Lucky.......if a guys willing to pay 2000 for a nx8, I say hunt for a used atacr for 2500 or so. The man who built my rifle recommends 3 scopes March tactical, NF ATACR, and Khales K line. He also tested may swaro X5 against his atac and found it to hold zero, there are a lot of spendy optics that haven't, you'd be surprised. Big braked light magnums with the recoil pulse and the the brake action jarrs a scope very hard, almost like hitting it with a hammer.
