Taliv isn't wrong in what he's telling you, but maybe it would help to explain some of the fundamental differences you'll notice between scopes, and how that will impact your ability to use it for your intended purposes.
For example, for the tactical and field shooting world a first focal plane (FFP) scope with a "graduated" reticle (MIL or MOA, your choice) is usually preferred. When a scope is built in the FFP the reticle will always cover the same amount of the target, at any magnification. This will give the appearance of a reticle "shrinking" or "growing" as you change magnification, but it will always cover the same amount of the target.
Your more conventional scope design (at least here in the states) is a Second Focal Plane (SFP) design. In these scopes the reticle always appears the same size as you look at it through the scope, but covers a different portion of the target as you increase or decrease magnification.
This is so easy to demonstrate in person, but it's a bit harder to describe in a text message. Maybe think of it like this:
You are shooting at 600 yards, or any long distance you choose, with a scope dialed to 10x magnification. Your buddy is watching your target with an identical scope that is dialed to 20x magnification. You take a shot and miss, and your buddy observes that your shot was 1.5 MILs to the right of the target, as observed on his own reticle. If you were both shooting SFP scopes then the amount of the "miss" observed in his reticle would not match the "1.5 MILs" you observe in your own reticle. If you were shooting FFP scopes, the amount of the needed correction would be identical, since the reticle is still covering the same amount of the target at both magnification levels.
Or, look at it this way:
You are shooting at a variety of targets at different distances during a match. The mirage is heavy, and you can't get to your maximum magnification without the targets appearing too blurry. Also, you are reducing your magnification for the closer targets, and to aid in acquiring targets at various locations (by increasing your field of view). With a first focal plane scope you will always view the sub tensions the same way. In other words, 1 MIL or 1 MOA will always be 1 MIL or 1 MOA, which corresponds to the adjustments on your elevation and windage turrets. With a second focal plane scope this is not the case.
With that said, SFP scopes are sometimes popular with shooters who are always shooting at known distances. In those scopes you can get a reticle that is most appropriate to your purposes (ideal thickness or thinness), without having to compromise between how thick a FFP reticle will look at maximum magnification, and how thin it will look at minimum magnification (in the SFP scope the reticle always looks the same from the user's perspective).
Anyway, I'm not sure I explained that very clearly, but suffice it to say that you should look into the issue of FFP vs SFP before buying a scope for long range shooting. Also, look at the different reticle designs to figure out what you might like. And, determine if you want a MIL based system or an MOA based system (make sure your turrets and reticle are in the same system… in the past there were many scopes with MIL reticles and MOA turrets. It's a plainly stupid way to do these things).
As far as reticles are concerned, there are hundreds of options out there, and it all depends what you want. Personally, I most often shoot at distances by dialing my elevation turret to compensate for the drop needed at any given distance. Then, I hold my wind calls on the reticle, rather than dialing the wind correction using the turret. I do this because it allows me to quickly adjust to changing wind conditions. For example, I was shooting at 1,000 yards yesterday, and had gusting winds that changed directions on me three times. In one shot string I had to change between a 0.6 MIL R windage hold and a 0.5 MIL L windage hold, all within about a minute and a half. Making these changes is easy on the reticle, and quick. As such, I have a reticle that allows me to precisely hold windage down to 0.1 MIL.
Another thing to think about is that scopes come in various tube diameters these days. The old school 1-inch tubes don't have a ton of room for internal adjustments, and won't let you dial as far out when you're shooting. More and more scopes are being offered in 30 and 34 mm tube diameters these days. Scopes will still vary in their amount of internal adjustment, but the larger tubes help. For example, I have a scope with a 1-inch tube that I run on one of my rifles, and it will max out the elevation dial by the time I reach about 800 yards with my .308 Win. With the 34mm tube on my Schmidt and Bender I can dial well beyond 1,000 yards without ever coming close to maxing out that elevation knob.
Magnification: Fixed magnification is simple, but limited. Variable magnification is nice for shooting in different environments, but more complex. I run a 3-20x scope, a lot of guys I shoot with run 5-25x, some run 3-10x or 4-16x, or whatever. Don't go too crazy on the top end of the magnification. You should be fine for most purposes with a top end of 20-25x. I've shot to 1,000 with 10x in the past.
Okay, enough with the "why are my needs important" answers. Here are a few scopes to think about, at different price points, mostly from lowest to highest:
Vortex Viper PST. It's a decent entry-level scope from what I've heard, and they have a great warranty. They make a FFP scope, and have some decent reticles. You can have these scopes for under $1000.
Steiner T5Xi. This is a new scope that will be released (probably) sometime this month. They're being made with high quality German glass, at a facility here in Colorado. I've been on a tour of their factory, and talked at length with the scope's design engineer. I really like the looks of this scope so far, and I think it will be a great scope for people who don't want to spend $3K on an optic. The reticle meets all of my requirements, and it has some unique features that I find attractive. You should be able to pick one of these up for less than $2K.
Nightforce. It's still a popular brand. The scopes are durable and the adjustments are solid. I'd rate their glass as a lower quality than Steiner glass (IMO), and they have limited offerings in FFP. But, they're still quite popular. Probably in the mid-2K range for a tricked out version (though it may be a bit cheaper — haven't looked at this in a while).
Schmidt and Bender. These scopes are one of the few at the very top of the heap in terms of scope quality. It's the clearest glass I've ever seen, and it's a nice solid scope. It has a zero stop, large adjustment range, some great reticle choices, and an overall fine design. I'm running one of these on my AIAX. I absolutely love the scope, but it was given to me as a gift by my better half. I probably wouldn't have thrown down that much money for an optic on my own, but I sure like the scope. They seem to go up each year, and I'd plan on a $3.5K purchase price these days.
Is a S&B worth a $1500 premium over a Steiner T5Xi, or a NightForce? That's for you to decide. Like anything else, you need to pay the basic price for admission to this game… after that it's a game of diminishing returns (you pay a lot for a little extra benefit at the top end of the game).
FINAL THOUGHTS:
Don't skimp on your glass, it's arguably much more important than the rifle itself. At one time I had my $3,500 S&B on my $800 Tikka. People laughed at me for running that setup, until they saw how well it shot.
But, if you don't have the cash now, don't think that you can't have a good time. My original precision rifle setup was my $800 Tikka with a $300 Weaver Grand Slam Tactical 3-10x scope. It shot just fine, and I had a lot of fun with it out to 700 yards. These days I'm doing even more demanding shooting, so I'm using more high-dollar equipment.
I have a night Force 3.5-15 NXS on my Remington 5R based .308 precision rifle and that sure is superb glass IMHO and built like a tank but not overly bulky. Premiers, US Optics and S&B ect. are out of my league , if I was an F class competitor tho ............
