Well, this is never an easy question.
First, we need a budget.
second, what type of shooting at 500-1000? Will it be unknown distance? Benchrest type? Just plinking?
The big problem you are going to have is going to be the up adjustment range. With .308, at 1000 you need a lot of up elevation. A 20 MOA or 15 MOA tapered base helps, but you will still need at least 60 MOA available. That is where the 30mm tubes shine, not only does the 30mm give better light gathering/transmission, but it gives you a much more adjustment ranges. But it is not required to go with a 30mm tube, there are some good 1" scopes that have enough adjustments. Including Sightron SII's, Some leupolds, Mueller, and some others. If you were willing to scale back to 800yards, the field greatly opens, as you only need about 40 MOA with a tapered base.
If you are doing extreme benchrest shooting at those ranges, you will want as much magnification as possible. But, I doubt you are, and you do not want to limit your flexibility by over magnifying your scope. For long range shooting, I generally recommend 1x per 100 yards you plan to shoot at. If you are going to 1000, then get 10x. Etc. This is not a hard rule, just kind of a rule of thumb. For a lot of 1000 yard shooting, 12x would be good, as would 14x. I don't recommend going above 16x. In fact, I'd scale back on power and scale up on quality.
MEL
First, we need a budget.
second, what type of shooting at 500-1000? Will it be unknown distance? Benchrest type? Just plinking?
The big problem you are going to have is going to be the up adjustment range. With .308, at 1000 you need a lot of up elevation. A 20 MOA or 15 MOA tapered base helps, but you will still need at least 60 MOA available. That is where the 30mm tubes shine, not only does the 30mm give better light gathering/transmission, but it gives you a much more adjustment ranges. But it is not required to go with a 30mm tube, there are some good 1" scopes that have enough adjustments. Including Sightron SII's, Some leupolds, Mueller, and some others. If you were willing to scale back to 800yards, the field greatly opens, as you only need about 40 MOA with a tapered base.
If you are doing extreme benchrest shooting at those ranges, you will want as much magnification as possible. But, I doubt you are, and you do not want to limit your flexibility by over magnifying your scope. For long range shooting, I generally recommend 1x per 100 yards you plan to shoot at. If you are going to 1000, then get 10x. Etc. This is not a hard rule, just kind of a rule of thumb. For a lot of 1000 yard shooting, 12x would be good, as would 14x. I don't recommend going above 16x. In fact, I'd scale back on power and scale up on quality.
MEL