The Standard Rifle Sight In
Dr. John Woods 02.29.16
Is there such a thing anymore as the “standard rifle sight in height?” It used to be that the textbook sight in height at the range for any centerfire rifle from the .223/5.56 on up to the big caliber game getters was three-inches high at 100 yards. Does this standard still work today?
The answer is, well, yes and no. For many centerfire rifle cartridges used for hunting moderate ranges, the 3-inches high at 100 yards is still a very useful starting point for zeroing your rifles. This counts for the universal cartridges like the 30-30, .270, .308, 30-06 .300 Winchester magnums and so forth. It can count for any cartridge if you calculate its range ballistics.
The trick is that the modern ammunition manufactured today is so precise and fine-tuned, that resorting to a “standard” zero may not be utilizing the full ballistic potential of the round you are shooting. The real proof in this standard zero is at really long ranges, when you want to be absolutely confident that your bullets are hitting the kill zone.
In order to take full advantage of your ammunition’s potential, you have to consult some factory ammo ballistics charts or use a ballistic analysis software package. You need to know the specific ammo you use, the exact bullet weight, and the muzzle velocity. It might also be useful to know the bullet’s ballistic coefficient. The higher the BC, the flatter the trajectory, generally speaking.
What you really want to know is where to sight your rifle in for the longer ranges at which you might be shooting. If your range is 400 yards maximum, then the ballistics information can tell you the drop of that ammo’s bullet at those ranges when sighted at specific height on the 100 yard range target. Then you extrapolate from there.
For example, pick the 30-06, 150 grain soft point bullet with a factory BC of .314. If sighted in at 1.8 inches high at 100 yards, it will be at 0 at 200 yards and hitting -24.4 at 400 yards. A ballistics software package will let you calculate to raise that sight-in height and also raise the drop at 400 yards. On paper anyway, this gives shooters a reasonable idea where their bullet is going to hit on a target out to extended ranges and in between.