Re: First long range rifle, what scope?
swfa SS 5-20x50, Weaver tactical 3-15x50 EMDR, 6-24 PST, Bushnell 3-21 HDMR are all in your grasp. I chose the Weaver tactical and have been pleased so far, great glass and repeatable clicks. The zeiss products seem to win the loyalty of most shooters that use them.
Couple of things to help you decide:
Internals, internals, internals. Vertical adjustment range will determine how far you can reach. Pay for internal part performance and craftsmanship.
Click adjustment accuracy and repeatability are essential to long range performance. Don't compromise on this.
If your scope fails you're done long range hunting. Warrantied or not I want my scope to perform first time, every time. Durability matters even more at long range.
MOA or Mrad or IPHY, if you aren't ranging with the reticle it won't matter much. Make sure the reticle and click adjustments match.
Glass is secondary, but also important. Glass appraisal is nearly the same as conventional hunting just to a greater degree. At extended ranges weaknesses in the glass or system are greatly exaggerated and can/will cost you the shot.
Using these parameters it is easy to understand why Nightforce is so highly lauded in tactical or long range shooting and almost never discussed in conventional hunting gear.