Scope Height

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

By differently I meant zeroed to different ranges. I didn't mean differently in terms of how many turns on the turrets are required. 

"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?"

This argument presupposes a condition in which we can all plainly see the high scope cannot possibly have enough travel in its erector tube to zero it, and then returns to holding the gun at an unrealistic angle which changes canting from a problem that manifests as a _windage_ error to a problem that manifests as an equal amount of windage and elevation error.

Indeed, I also like to explore extreme scenarios as a way to probe the potential effects of some variable on a smaller scale. However there is some amount of constraining the conditions that is necessary to make what is already contentious subject into one that can be explained and digested. Changing cant to both a windage and elevation problem is not useful in that respect. 

"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.

I am not assuming a single distance. And I can't fault you for believing the article on AccurateShooters because I took those arguments as gospel for a long time, but just because something is presented in a professional manner does not make it true.
 
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Nation,

To get back to the original question at hand......

One of the main reasons for higher and higher scope mounts is simply this....

In Field Target competition, all targets are between 10 and 55 yards. When one has a given scope mounted at, let's say 1.5 inches above the center of the barrel, and you have a zero of 30 yards. Those are your givens. Your apex of your pellet is 30 yards as well. So, your zero is your apex, and all of your adjustments on your scope are all up, at all distances. On most higher end scopes used for Field Target (Nikko Stirling, Sightron, March, Schmidt and Bender, ) the amount of clicks from zero to 55 is around 80-90 clicks at this scope height. This puts your 55 yard click solution over 1 elevation turn out, in order to hit 55yds.

Now, raise the same scope to 2.5 inches above the bore, and use the same zero of 30 yards. You still have a zero of 30 yards, and 30 yards is still your apex of pellet flight. Now, in order to hit 55 yards, you only need about 45-55 clicks to reach it, and all of your Field Target distances are all within 1 scope revolution, avoiding the problem of loosing track which revolution you are on. Most scopes mentioned above have 74 clicks (or less) per revolution. Thus, by raising the scope height, you keep all of your Field Target clicks within 1 revolution, and this will eliminate any confusion on the Field Target battlefield, of wondering if you are a revolution out or not.

Tom Holland 

Field Target Tech 
 
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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.
Click to expand...

<bows with respect>

Oh no problem. You've been very cordial, sticking to the argument, making your points. That's great! It's only when personal attacks and snide remarks start flying that I lose interest. And I don't want anyone giving me a pass on a subject on the basis that I've been helpful or correct on some other thing in the past. Hold my feet to the fire. I wouldn't want it any other way.
 
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...

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".

Click to expand...

It's physics/trigonometry.

It's a function of the bore-line direction and trajectory, not the shooters perspective (scope - line of sight). Gun cant errors are not affected by scope height.

Slower pellets take longer to reach the target. The longer the time of flight, the more drop. Cant error is a function of drop and cant_angle.

This is what you get with gun cant:

horizontal error = drop x sin(cant_angle)

vertical error = drop x (1-cos(cant_angle))

"… 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?"

Answer: Yes

"...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...."

That is not cant error. That's a ranging error (from the shooters perspective), and it is affected by scope height. Different height scopes have different lines of sight. They converge at the distance they are zeroed for (be it clicked to center or the correct mil-dot for holdover). The farther you get away from that zero point, the greater the divergence of the two lines of sight. When they diverge significantly, the shooters perspective on the miss is different for the high and low scopes.

The line of sight plays into distance (ranging) errors regardless of cant. Most FT shooters are very aware of ranging errors vs scope height.
 
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I hunt with my air gun.i dont adjust the turrets before every shot in fact after setting zero i dont touch them again. For me, i hope most can grasp the advantage of having my line of sight and bullet path close together as possible for as long as possible. When I hit the woods i have to guess yardage and angels quickly i dont have time to range targets and adjust turrets. Of course comfort and a repeatable position figure in and matter too, but for me i want the scope and bore close together as practical. As my scope and bore distance increase my range to target guesses become less and less forgiving. Because of this i mount my scope low as possible often.going to a 30 mm instead of a 50 mm because at the distances i shoot, field of view to me is less important than distance of scope and bore. Just what works for me and why to me distance between matters.






 
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uh,I get now,I truly believe in instinct shooting,most all trick shooter do it,fact is you really do not need sights per say,after shooting tens of thousands of rounds over many many years it became a reflex thus instinct shooting....you can judge distance ,drop and all others things.

I think many of us have seen the movies of the great instinct shooters ,none I have witness use scopes.

You can do the same thing with a scopeI thou I think at shorter ranges a scope can be be a waste for such antics.

I do get your point,so I am guessing you also use lower power....what about using a "scout scope" .

I used open sights for the first 25 years ...nowadaysI almost need a scope.

I was at the Richmond rifle range and watched a 100 yd match...they used M1 and M14 shooting off hand with open sights,can you image how hard that is?



if you have not guessed it I do have ADD and shooting helps me focus ..for longer periods of time.
 
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Nation,

To get back to the original question at hand......

One of the main reasons for higher and higher scope mounts is simply this....

In Field Target competition, all targets are between 10 and 55 yards. When one has a given scope mounted at, let's say 1.5 inches above the center of the barrel, and you have a zero of 30 yards. Those are your givens. Your apex of your pellet is 30 yards as well. So, your zero is your apex, and all of your adjustments on your scope are all up, at all distances. On most higher end scopes used for Field Target (Nikko Stirling, Sightron, March, Schmidt and Bender, ) the amount of clicks from zero to 55 is around 80-90 clicks at this scope height. This puts your 55 yard click solution over 1 elevation turn out, in order to hit 55yds.

Now, raise the same scope to 2.5 inches above the bore, and use the same zero of 30 yards. You still have a zero of 30 yards, and 30 yards is still your apex of pellet flight. Now, in order to hit 55 yards, you only need about 45-55 clicks to reach it, and all of your Field Target distances are all within 1 scope revolution, avoiding the problem of loosing track which revolution you are on. Most scopes mentioned above have 74 clicks (or less) per revolution. Thus, by raising the scope height, you keep all of your Field Target clicks within 1 revolution, and this will eliminate any confusion on the Field Target battlefield, of wondering if you are a revolution out or not.

Tom Holland 

Field Target Tech
Click to expand...

The extra height also allows fewer clicks for far targets and more clicks for close. Ranging close targets is easier therefore the advantage of high mounts.

Also IMO the best scope for Field Target is one with 1/4 clicks. This allows for all 10 to 55 yards in less than one elevation knob revolution. My 1/4 click scope is Schmidt and Bender 10-50.
 
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At my avanced age scope is a must. I do have a pb set up with a scout rig. Great for moving target, not any real down side,but most guns not set up for. Not any better shot than anyone else but yeah at 40 or 50 yards dont see any need for much over 6 power. Just want original poster to know he is not the only one. And try to explain why i feel as i do. Shoot what you like and have fun doing it, try not to get offended by some old fool and his ignorant opinion. 
 
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Don,

Yes, you are correct. All of those scope brands that I mentioned above that have 1/8 minute clicks that are mounted low to the barrel, will not get all Field Target distances within 1 revolution. Raising the height an inch or so, usually gets it within 1 revolution. This is one reason why I went with the Kahles FT scope. It has 1/8 minute clicks, but it has 138 clicks per revolution. I only use 1/3 of a revolution for all my Field Target distances. 

Tom Holland 

Field Target Tech 
 
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