I suspect abuse that NXS scopes handle during military duty is at least as brutal as what your horses will dish out. In the 2008 catalog they are showing an NXS that has an AK47 bullet hole through the tube and it was still able to function. If the Seals don't worry about cover caps for the NXS then you probably do not have to either. Seriously, they are about as close to bullet-proof as any turret, trust them. Your horses will give you a lot more grief than the Nightforce. Suggest you consider a 3.5-15x50 with zero stop and NPR-2 reticle. Very slightly smaller, nice to leave the scope on 15 and come down, better than finding out that you rarely use 22 power but usually use 15.
Good luck with your scope selection and welcome to LR Hunting.