Hey there, I thought I would chime in on this, as I went through this process about 2 years ago. I am not, by any means, a expert or guru. I'm just a guy with some Military experience and now an avid shooter. So with that said, it looks like you have a good magnification range for a "SPR". 2.5-10 or 3-9, maybe even 2-8 depending on how you're going to use the rifle. Right now, I am very happy with my SWFA SS 3-9x42. In fact, its one of my favorite scopes to this day. I suppose that would be due to the fact that I've used much more expensive and inexpensive options. I get this little fuzzy happy feeling when I go to the range and see guys with scopes as expensive as my Jeep and I'm getting more hits with a $500 scope. Its this weird conception that some people have; They feel like if they spent $1500, $2000, or more on a scope that their gun is better than yours. In reality, your rifle is only as accurate as you are. (Same concept with Jeeps, motorcycles and many other things) And with rifle scopes, if you spend $1500 instead of $500, you are not getting a scope that is 3 times as good, you're just paying 3 times as much. In reality, you would be lucky to get a scope that is 1.5 times "better" than a scope that is 3x as expensive. And even that is debatable. Everyone eyeballs are different, so as long as you have a durable and repeatable scope, you will get hits. Just look at WWII "Snipers", those guys used scopes that, compared to today's rifle scopes, are probably no better than the scope on your pellet rifle. They still got kills way out there. Now, if you only have a couple of rifles, you have all the other essential gear for the type of shooting you want to do, and your budget is around $1500... You might as well get the best scope you can for the money you have to spend. But, like I said earlier, your rifle is only as good as you are. So practice is more important than whats sitting on top of your rifle, generally speaking. Nightforce 2.5-10x44 is a great scope, but its not FFP. I would say for probably 80% of guys shooting a SPR in the role its intended to be used, FFP is probably better than SFP. With training, you can get around SFP just fine. I like a simple mil dot/hash reticle. Never been a fan of BDC reticles, given the fact that I run different loads often and shoot at different locations and conditions and don't ever seem to get good impacts utilizing a BDC reticle. You might be in a different circumstance than me, and can manage to use BDC Reticles just fine. This is something, along with SFP, that you can overcome given your preferences and circumstances. For me, FFP and Mil-dot based reticle is the easiest way to do what I want to do.
I know this got off the topic of whether 42 obj and side focus is worth $500. And I'd say no. Unless you're hunting dawn/dusk and find yourself in extremely low light, and need 10x magnification in those conditions, its not worth it. You can always go down to 5x and just know that since you're using SFP, you're observed impact corrections are roughly twice of what they would be on 10x. Then again, its going on an AR in .223, so a follow up shot with holding instead of dialing would be faster and easier. Your exit pupil would be around 6.4mm of light at 5x magnification, which is more than enough. 5x is enough to clearly identify a target at 200 yards at night, not to mention .223 isnt a cartridge I'd feel comfortable hunting with much further than 200 yards, unless its varmit or something similiar. The other thing when you spend big bucks on a NF, its probably going to be a little bit better than your average $500 scope with similar magnification and objective size to the Nightforce in low light performance. So even with less than 5mm of exit pupil, it would be a tad clearer and possibly brighter than a $500 scope.
Again, I'm not trying to totally steer you in a different direction, I just don't want you to spend lots of money on a scope, and not have money to train and get the gear you need for "precison shooting". Just about anyone can walk a rifle out to 600 yards, but to know your system, and get a cold bore shot at even a known distance is pretty impressive. unknown distances in wind are even more difficult. I had a NXS F1 on my "SPR" for a little bit until I got more guns and needed more scopes on different tools. I'm just saying, if you don't have much experience, you might be better off with a lower priced optic so you can have more fun!
This is a great resource of much more experienced guys than myself and I would recommend doing some searches and reading what others have to say.
Hope I can help you out here.
