Years ago I just sighted in the rifle at 100 yards then based on the caliber just added either 1 1/2 or two inches up for my zero and considered it good out to 200 yards. Sometimes that worked, but more often than not it resulted in misses at extended ranges. Then one day after missing what was thought to be a 200 yard shot with my trusty 308 I started thinking about the differences between competitive shooting with the M-14 we were issued, and how I was treating my bolt action Model 70, 308 and suddenly knowing that I was missing something, pondered what the differences were. After numerous hours, days and weeks thinking I woke up from a sound sleep at 0230 hours on a rainy Thursday night when a loud clap of thunder and the bright light from a lightening bolt hitting the tree in the neighbors yard next door (true story) the proverbial light bulb illuminated , my hair standing straight up (due to the electromagnetic field from the lightening) and the differences between match shooting and hunting that I had been doing for all these years came to light. When shooting rifle matches, with iron sights we had a different zero for each different range, 200, 300 and 600 yards that we cranked into our sights even before we thought about wind, light and mirage. Why did we do this? Because the rifles shot differently at different ranges. We were shooting National Match versions of the M-14, heavy barrels, match sights which gave us the ability to make 1/2 moa elevation changes, and the normal 1 moa windage adjustments using our issue Lake City Match ammo. Lake City match, was some of the most accurate ammo that I have had the pleasure to shoot. We literally shot thousands upon thousands of rounds of the ammo, all coming from the same lot produced at Winchesters Lake City munitions plant. Same lot number, meant same characteristics and no need to change zeros due to different ammo lots.
So how did this relate to me and my trusty Winchester. At the time I had a Bushnell 3 - 9 on the rifle with the usual capped elevation and windage adjustments. The optic quality was OK, but nothing to write home to Dad about. I took it out to my friends farm where we could put up targets out to 300 yards, which we had never done before. Started out with last years zero and ammo and fired 3 shot groups at each range using that zero. As expected the rifle was lts sighted in 2 inches high at 100 yards, when I moved to 200 the group was expected to be dead on at 200 based on the predicted bullet drop. Instead of being right on at 200, it was 4 inches low and 9 inches to the left. (no wind condition) Then on to 300 yards. had the scope set to 4X which I was comfortable with at 100, it was OK at 200, but could not see the center of the target well enough due to the glass and apparent smaller looking target. I cranked the scope all the way up to 9X. Could see the target better, but still not great. By the known bullet drop theory that the rifle had been sighted in with the hits should have been around 8 inches low at 300 yards. Instead of being where expected the hits were off the target and out on the cardboard backer (48 x 48 inches with the target centered) The group size was not the issue, it was around 4 inches, for a hunting rifle at 300 yards would be more than adequate if the bullets hit where aimed. The issue was that the group was hitting 18 inches low and just catching the edge of the backer on the left side at 24 inches left.
This brought up the reasons for different zeros at different ranges when target shooting. I checked to see what the specifications were when the bullet drop chart on the ammo box was. It was a 26 inch barrel that was used when they set the bullet drop and velocity at the different ranges. My trusty Winchester only had a 20 inch barrel so nowhere near the performance on the box. Problem 1, bullet drop solved. not 100% sure on the difference in windage, I have been told that it has to do with barrel harmonics, which with a fixed reticle we dutiful zero the hit at 100, but it does nothing to change the different point of impact at greater ranges.
It was at that point where I decided to open the purse, watched the moths fly out and plunked down the cash for a new Vortex Diamondback Tactical 6 - 24 x 50. I now have tactical scopes, yes all Vortex on all my rifles from .22 up to 338 win mag. The Tikka T1x .22 and Winchester XPR 6.8 Western have Diamondback tactical, my Tikka T3x 270 and Remington 700 338 Win mag, my primary hunting rifles both have Vortex Strike Eagle 5 - 25 x 56 scopes on them. Lens clarity is crystal clear, light gathering under low light conditions, which is where I hunt in a valley morning light comes late and leaves early is great. The tactical reticle is also illuminated brightening up the point of aim under all conditions. The turret caps are all adjustable so you can return back to your initial zero with the elevation having a turret stop at your zero setting so you can't roll the scope down beyond your zero.
This year when sighting in both at 100 and 200 yards both the 270 and 338 had completely different zeros with changes noted so that the rifles are dead on at the normal distances I shoot at. While this does not compensate for wind conditions which are tricky with shifting winds anywhere in the valley being difficult to sometimes read or change throughout the bullets travel, If I miss, it's because I messed up and it's not the rifle or ammo's fault.
My advice is to take the time to see how your rifle really shoots. Even with conventional turrets if you leave the caps off, zero the turret to your rifles zero you can shoot different ranges noting the changes in windage and elevation, write them down and reach up and crank in the changes if need be. The trophy buck that crosses your path may become a wall hanger in your home, rather that still running in the woods after the shot that missed.
