Thread: scope sighting

Well I used a 200m zero for decades on the 303 and it was never really good. Since most of my shots were between 50-150m (slips on North Island creeks and rivers) I always had to hold low. How low ? Always guessing a bit.

Once I changed to a hundred metre zero with a 7mm08 I could shoot from 30 to 130m with less than a centimetre departure from the crosshair and my success rate increased a lot. Beyond 150m I can dial, but it would also be OK to hold over. "Is it closer to 200m or 100m ?" "More like 300m than 200m ?" I'm not very good at range estimation, I know that from using a laser often, but even i can guess those.

There is a fallacy with the 6" tube idea: that you can shoot as far as the 6" (15cm) rise/drop "point blank range" by holding dead on.
Essentially, your rifle group size goes on top of that and your marksmanship error on top of that. (They are added by root-mean-squares, to be mathematical). For example, if your drop from point of aim at 250m were 4" (10cm) and your target were 8" across, then only the top half of your shots would land in the target. Who wants to accept a 50% hit probability when you've fired a good shot ?

Much more reasonable would be an acceptable range-drop error of 2" (5cm) at your max range, which should be only 200m if shooting without a range finder. If you do use a range finder and a simple drop chart, you can take almost all that source of error out and just concentrate on the hard stuff - hold, release, perhaps wind past 200m.

It is good to sight in at 25 or 50m because you will always hit an A4 paper so not waste any ammo. You just need to know the required point of impact for your 100m or 200m zero distance. It varies a little with your velocity and a lot with your scope height. Also you do need to check every now and then just where the shots actually pattern at 200m or 300m. That also gives you a reality check for how small an animal you can truly shoot under optimal range conditions. Don't rely on a calculated drop value when shooting at live animals. You should only shoot as far as you have verified on paper.

It is not good to use the full kill zone size, when calculating a "point blank range" .