have you looked or considered Ziess ?
my dad has the NX8 on his gun and I have a Ziess conquest v4 both are awesome and obviously the NX8 is a first focal scope and the V4 is a second focal plane so that will probably affect your decision.
but that being said I really like the Zeiss Conquest V4...
loading for a longer barrel length what have you found as far as burn rate is it better to use a faster burning powder or slower burning powder to achieve velocity without over pressuring ?
I have a 338 RCM built on a Montana Rifle Company 1999 Action with a 27" Krieger 1/10 twist barrel it shoots very nice and is a pretty impressive cartridge for a compact magnum.
I setup it with a 10 MOA rail and a Zeiss Conquest v4 6-24×50.
I've been shooting the hornady superformance 200 grain...