Now that I've got my first AR coming to me in the mail, I've started looking at scopes/optics that I am considering purchasing. The rifle is a S&W M&P15OR and I'd like to use it more for getting into the longer range target practice, so preferrably something with some zoom to it (though I have no idea what is a good zoom range for all around use). I don't know much about scopes and the more research I do, the more confused I get. Hypothetically, at the moment my budget is $500 as I can't see myself paying more for a scope at the moment until my longer range use can no longer be achieved with the $500.
In my research, I've found the Nikon M-223 4-12x42SF with BDC 600 reticle. Seems to be relatively new, so it's been hard to find reviews for it, but I like the concept of the BDC reticle. Does anyone have any opinions on this scope, handled it, shot with it, read a review on it elsewhere, or have another recommendation that is along these lines?
In the end of things, I'd like to get a quality scope that I can keep for years and transfer between rifles (as I see myself getting another rifle eventually), that has a mil-dot style reticle (as opposed to just crosshairs), windage and elevation adjustments. I've always had the mentality that if I pay a bit more now (better than entry level) it will last a bit longer, so as long as it's a quality scope, I might be able to justify spending a little more. At the moment, I'm slowly specing out an SPR for long range shooting, so it'd be really excellent if I could get a scope now to use for both rifles.
Thoughts? Opinions?