Scope Height

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Spartan

Spartan

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Jan 18, 2020
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Why do airgun manufacturers (and airgunners) seem to keep pushing scopes to be mounted higher and higher relative to the bore? I get that magazine capacity—and the magazine's placement under the scope—was a driving factor for a bit, but that doesn't appear to be a limiting factor anymore. I find myself avoiding airguns that seem to unnecessarily force high scope mounts, such as the Veteran, Hatsan's new offerings, and almost everything FX.

I feel that I am now in the minority for wanting my scopes mounted as low as possible to keep the best point blank trajectories when shooting at ranges less than 100 yards, and for must hunting purposes. Does anyone else feel this way, or am I just off base here?
 
I am with you and prefer my scopes mounted lower if possible. But It depends on the gun. I tried a lower mount on my Impact but it made me twist and tilt my head in a way that was very uncomfortable. So I ended up with higher mounts that are a much better fit. It does not seem to make much of a difference at ranges of more than 10 or 15 yards. At near ten yards or less there is a bit of holdover required though. More than anything I just needed to get over thinking that it really made a difference how high the scope was mounted. Because it really doesn't as you get used to it in short order.
 
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At one time I also liked the scope as close to the bore as possible. For one thing the higher the scope the more likely there will be errors due to canting the gun. 

One problem with the lowest possible scope mount, especially with mid powered airguns is that you only have one usable "zero" yardage range, say from 30 to 40 yards for example. Everything before and after that will be low. At over 70 yards it could be really low.

With a higher mounted scope you actually have two "zeros". For example 30 and 60 yards. Between those distances your POI may be an inch high. And in the yardage ranges of 20 to 30, and from 60 to 70 you may be an inch low. So to sum it up you would have a two inch "kill zone" from 20 to 70 yards. You would need to estimate your yardage and use a little hold over/under, but for me at least, it's an easier way to put a pellet where you want it.
 
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Yes, I looked up the article and read the context and the first statement is correct. The second one is not. It is a very common and often-repeated misconception and it will therefore be difficult to eradicate, however this author documented a detailed test to settle the subject so we can all see for ourselves. http://www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html

By the way, the article also shows two bubble levels designed to attach to the scope rail. That type of level will only function as intended if everything else on the gun is mechanically near perfect...scope perfectly centered over the bore, barrel perfectly straight, bore perfectly centered on the barrel’s OD, rail machined perfectly parallel to the barrel mortise, and so on.

One particularly common source of error is the scope not being centered over the bore, especially with 11mm and 3/8” dovetails and their variability, and the use of tip-off rings with reversible clamping plates. However this issue is completely erased by slightly twisting the scope in the rings such that the reticle intersects the bore.

Thus a scope-mounted bubble level is a better choice in most cases because it can be easily indexed to correspond with the reticle (and therefore with the force of gravity acting on the projectile).
 
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So you're saying... If I had 2 identical guns, but one had a scope mounted 1 inch above the bore, and the 2nd one had a scope mounted 1 foot above the bore, and for the sake of argument let's say both are zeroed to a POI at 100 yards. Now if both guns are held at a 45 degree angle and the crosshairs are on the target do you believe both guns will impact the same distance from the bullseye? I would certainly bet a friendly beer on that one.
 
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I thank you for the beer 😀

Consider this, I manage to set up a rifle with two scopes, one above the other. I have both of these scopes zeroed to the same yardage, say 50 yards. What happens to each of their mildots? They superimpose onto each other. Thus the point of aim, let’s say 4 mildots down for the target I’m shooting at 100 yards, is exactly the same for both scopes. As a result, whatever amount I miss my point of aim by virtue of tilting the rifle, I miss it by the same amount whether I’m looking through the upper scope or the lower scope.
 
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Before you make a choice on that beer...

Let's start with the scope that is1 inch above the bore. At 100 yards the midpoint trajectory (the curve of the bullet that goes UP over the line of sight, then DOWN, due to gravity), may be 3 inches, for example.

Now the scope that is 1 foot over the bore will never have the bullet pass over the line of sight. It will always be under. 

Let's assume both scopes were brand new when mounted on the guns. Both would be optically centered. To zero the lower scope, you should be able to do it with the up/down turret. To zero the 1 foot or higher scope you will run out of the "UP" adjustment. But let's say you could.

Now let's shoot our 100 yard zero'd guns, with a 90 degree cant, out to 200 yards for the heck of it. OOPS! Looks like the higher one with all that adjustment is shooting over to the next county.

Yea the angles of cant and height of the scopes depicted are really exaggerated, but it helps to visualize situations where subtle differences are just that, subtle.
 
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Okay I see where you're going with that. If the bullet "rises" 3 inches, it never crosses the line of sight of the 1ft-high scope. Yes if we assume the two scopes are both pointing straight ahead, your example holds true. That is, if we make the assumption that the scope bodies (their tubes) establish the line of sight. But they don't. It is the erector tube inside the scope that establishes the line of sight. So this example only holds true if the two scopes are zeroed differently. As soon as we zero the higher scope the same as the lower scope, their mildots superimpose on top of each other. Since the mildots are the things we use as our aim points, and cant error is the amount by which I miss the target compared to my aim point, their errors are the same.

Perhaps it would be helpful to think of the aim points (the reticle) as something that is projected onto the target rather than the thing that's inside the scope just 3 inches away from the eye.

Now for the scenario where the gun is canted 90 degrees, I agree that will yield different results because we've just changed the elevation turret into a windage turret. Here's why we can't draw conclusions from that. For the modest angle at which a typical shooter will hold his gun, canting results in an error that is overwhelmingly horizontal (windage). There is a very small amount of vertical component to it that for all practical purposes can be ignored. See Perry Babin's demo animation at http://www.arld1.com/impactpointvscantangle.html to see what I mean. Notice you have to hold the gun at an absurd angle before you begin to get any meaningful change in elevation.
 
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But this mildot superimposition scenario would only hold true at the exact range that the scopes are zeroed. If you zeroed at 50 yards and then used mildots to shoot at a target at 100 yards in your scenario, the mildots of both scopes would no longer superimpose at 100 yards due to the top scope having a higher attack angle. The mildot cant radius for the top scope would be larger than the bottom scope in every scenario other than at the point where both scopes are zeroed.
 
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But this mildot superimposition scenario would only hold true at the exact range that the scopes are zeroed. If you zeroed at 50 yards and then used mildots to shoot at a target at 100 yards in your scenario, the mildots of both scopes would no longer superimpose at 100 yards due to the top scope having a higher attack angle. The mildot cant radius for the top scope would be larger than the bottom scope in every scenario other than at the point where both scopes are zeroed.
Click to expand...

That's an astute observation! However at any usable scope height, the angle is so small as to be insignificant. Unless you're a giraffe :)
 
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You said: "So this example only holds true if the two scopes are zeroed differently. As soon as we zero the higher scope the same as the lower scope, their mildots superimpose on top of each other".

Of course a higher mounted scope is going to be zero'd differently than a lower one. How could they not?

Explain how 2 scopes, one mounted an inch above the bore, and one a foot above the bore can be zero'd the same at a target 10 yards away. One prints an inch below the target, the other a foot below the target. The foot high mounted scope may need 50 or more turns of UP on the turret. With 50 turns of up on your scope, compared to one that has half a turn, go see what happens with a 45 degree cant at a target 100 yards away. What would the MILDOTS say in a situation like this?

I'm beginning to think your explanations and interpretation of mildots are based on the premise that there is ONE and only ONE yardage to be considered. It may actually be true for that situation. But as AccurateShooters.com explained: "cant error increases with distance, and second, cant-induced windage errors are worsened by mounting your scope high above the bore axis".


 
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When you said: "That's an astute observation! However at any usable scope height, the angle is so small as to be insignificant".

An insignificant error of .1mm can be the difference between a 10 and a 9 on a score card.

Nervoustrig, I apologize if I'm sounding argumentative. I've always respected your advise and opinions on topics here. Go ahead and have a beer on me! Thanks for your posts.


 
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But this mildot superimposition scenario would only hold true at the exact range that the scopes are zeroed. If you zeroed at 50 yards and then used mildots to shoot at a target at 100 yards in your scenario, the mildots of both scopes would no longer superimpose at 100 yards due to the top scope having a higher attack angle. The mildot cant radius for the top scope would be larger than the bottom scope in every scenario other than at the point where both scopes are zeroed.
Click to expand...

That's an astute observation! However at any usable scope height, the angle is so small as to be insignificant. Unless you're a giraffe :)





You crack me up
Click to expand...


 
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another boloney sandwich please....in reality most shooters would not notice,it is just another half truth that can be proved either way.

Large bells in higher mounts,of course.

I was shooting yesterday with same rifle I have been shooting for weeks,I noticed my "cheek wield "was a little off,I was having to "crunch" my neck down a little too much for comfort and consisent placement ...my mounts were not high enough ,simple as that.

Sure I have been reading about scopes and barrel mounted close as possible....sure sounds good to me,butt I also like to be practical about such things....what works for you may not work for me ...the more comfortable I am the better I like it.

Bad eating habits affect your shooting ability more than high mounts.Oh yea I like to have an adjustable butt pad too.














 
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