Home Forums Hunting & Shooting Ask The Gunwriters Ask John Barsness Questions About "SCOPE HEIGHT."

Sorry about the late answer fellow, but I wanted to write it thoroughly, and this has been a long story...

First about my theory:



I think this is all clear and logical. Let me mention that the 'd' drop value has nothing to do with scope height, bullet drop is only about the bore and projectile. Ballistic softwares need the scope height only for the trajectory calculations but not for the drop value. Drop at a given distance depends only on the muzzle velocity and the real BC value (which can be measured under the given environmental conditions).

About zeroing, this was an interesting question and lead me to some interesting conclusion...

First we have to define what 'zeroing' is. I assume that if you talk about zeroing then you mean that your rifle shoots at a certain X and Y distance (1st & 2nd zero) exactly where the crosshair looks and you hold over/under for the other distances. And when you talk about line of sight then you mean the line where the crosshair centre looks.

These concepts are common in shooting scene but I would rather say that zero is where we aim and where we want to hit, so the rifle is zeroed at a given distance when I know how to look through the scope in order to hit the target.

Anyhow, the thing is that if you use an other aim point, say a mildot, you use an other LOS which looks exactly to the target. The LOS is always pointing at the target, this is the trick. You adjust the line-of-sight (when shooting with clicks) or select from many pre-defined lines (when shooting with mildots). And then the bore line has to look with 'd' above so the bullet drops into the target etc.



So we know already that if we shoot with clicks or mildots (i.e. we do the required correction of LOS with our scope), the canting error is totally independent from the scope height.

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But now comes the twist! You have to know that I'm shooting FT and we usually align the LOS to the actual target with clicks or a few people use mildots, but whichever way, our LOS looks at the target and if we cant, we rotate the bore line around the target itself, see above.

I considered that all of these 'high scope is bad' opinions come from firearm shooters. Maybe they do anything other way which can change the things? And yes, they do.

I had to revise my stand. Still standing by all written above, I examined the third aiming method when one shoots to another aim point with the appropriate distance above the target.



The main difference is that when canting the rifle, the rotating axis of the bore line is not at the target but at the aiming point (e.g. the back of the ram). And in this case, the higher scope causes a bigger canting error, indeed.

So if we shoot with holdover measured at the target (i.e. we do the correction outside of the scope), the canting error grows together with the scope height (assumed that all other parameters are the same).

John, now I'm gonna tell you the result of your experiment already: if you aim with clicks or mildots at the two ranges then you can't get more difference than the grouping size and wind effects. But if you measure the hold-over on the target then the higher scope will give more canting error. Funny but both results would have been correct, depending on your shooting style.

I believed that the question is that the higher scope DOES or DOESN'T result a bigger canting error but the real answer is that it MAY, with certain aiming techniques.

Thanks for the cooperation my friends :-)