I need a new scope for my 18” 5.56 DMR. I am torn between the two options from NF. I usually don’t like to go below 18-20x on my scopes but I see a lot of love for the ATACR, for obvious reasons. Both would be bought with a MIL-XT and cost around the same +\- $400
Any substantial optical quality I would be giving up by going with the NX8?
Which 4-16 ATACR are you referring to?
The 42mm objective version is a totally different animal compared to the 50mm version.
NX8 is a tad physically smaller but at the cost of an unforgiving exit pupil, more critical eye relief envelope and definitely a much shallower depth of focus when compared to the 42mm objective version of ATACR.
You didn't mention whether the NX8 you are considering is FFP or SFP so I'm assuming FFP.
If FFP, I double dare you to use any of the reticle features while in the low end of your X.
As with a lot of the FFP scopes, the very reason you justified them over SFP is nullified when you are using the lower end of your magnification. This problem is more prominent as you look at FFP scopes with 1:8 and 1:10 ratio mag ranges.
The NX8 line is one that I really wanted to like when they were announced but in this case, I would vote for the 4-16x42