Even my 17Mach2 can shoot squirrels past 125 yards. The Mach 2 is 200-300 FPS (depends on ammo) slower than the HMR. I have shot ground squirrels out to 144 that seems to be the max for this cartridge. Shot on paper out to 140. The group seems to open up, after that point with the Mach2.Trajectory is definetly not a problem, at 150 yards my bullet drop is still above the thick part of my duplex reticle on 14x.
I remember shooting pop bottles with dads HMR at 200 yards. They are just tack drivers. The cool thing is even if its windy, you can see your misses through the scope then correct with a follow up shot.
Ol' Mikes right about magnification. I have a 4.5-14x on my Mach2, I wished I had more power. I can see great for hunting, but when I do target work I would like more power. Dads HMR has a 3-12x, it works for him because he dosn't "go long" because of his poor eyesight.
The most benificial thing I did was lighten the factory trigger. Ruger triggers are HORRIBLE, It is now stoned down to 1.25 pounds.