It depends on the scope you choose. Pay ATTENTION to the TOTAL MOA of a scope, then go for about 1/2 or less MOA for a rail for distance. And 'real long shots' may call for more MOA on the rail ? I'm not sure since I can only shoot ca 200 or less. Try to talk with 'long-range' shooters at your club. My Athlon Argos 8-34x56 FFP Only has 40-ish MOA TOTAL so I needed 20MOA going out to 175, and I had to rely on 'hold' at 20X to see the target at that distance. 34X reduced the visible reticle too much to see the target. I DIDN'T PAY ATTENTION TO THE SPECS when I bought the scope, and wasn't aware of the "1/2 MOA " guideline. It cost em $175 for Burris XTR rings, but better for the distant option than changing scopes OR changing Rails. YMMV - BE CAUTIOUS.