Hi Folks:

John Barsness's latest exclusive Campfire column, "SCOPE HEIGHT," is on its way to all email newsletter subscribers. If you haven't received this or previous versions, please PM me your email addy, and you'll be on board for future monthly columns.

This is the place to ask John questions about his column. So let 'er rip.

Don't forget to check out John's (and Eileen's ) other great stuff at http://www.riflesandrecipes.com.

Many thanks, as usual, John!

I've PMed rick asking to get on his email list with no response (I used to be on the list). Still no link to the article. Any chance someone could post a link?

Same here. I also PM'd Rick to get back on the list I thought I was on, but no response. Where can I link to the article?

My guess is that Rick is on spring break from the California school system. I sent him another column a few days ago and haven't heard anything, and he usually responds right away.

Try this:

http://www.24hourcampfire.com/newsletters/February_2011.html

Thanks!

Good article, thanks.

I had often wondered scope height-low mounting and why it was important to a lot of riflemen. For my style of hunting, (close quarters dense woods) a scope that comes up on target without a lot of head bobbin, movement, stock crawling, and weaving is more important than being concerned only with a low mount. My features seem to require at least a medium mount on most rifles to achieve this.

I agree with everything in the article except for the opening line about Redfield making the first "practical" variable scopes in the 1960s.

According to the Shooters Bibles I have from the early 1960s ,Redfield did not even have ANY variables on the market as of 1962.The only thing Redfield listed were the Bearcub Fixed power scopes in 2.75, 4 and 6x.

Both Leupold and Bushnell had 3-9x scopes out by 1962 that look pretty much like any 3-9 variable sold today. The Leupolds were the very first "Vari-X" models. They were listed as being continuous variables with fog proofing and have internal adjustments. Unless they did not have centered reticles (unlikely by 1962), they would have been as practical as any other hunting scope of that era.

The first Leupold variable (which did come out in 1962) did NOT have constantly centered reticles, and didn't for two years. Redfield introduced their 3-9x in 1963--with a constantly centered reticle.

Well, there you go...That explains your viewpoint.

I am agreed that a constantly centered reticle makes all the difference in terms of a practical variable. I wonder when the Bushnell scopes had centered reticles?

A bit late I discovered the same thing -- for almost all of my rifles, medium rings give me a better instant sight picture.

Not sure whether it pre-dated the Redfield or not, but there were a lot of Bausch and Lomb 2.5 to 8x's around here back in the early 60's. Nice scope with good optics and a finely tapered reticle, but the external mounts were a pain the ass to adjust. The main selling point was that you could easily switch the scope from one rifle to another and back again if you had the B&L mounts on each gun.

Yeah, the B&L was made in the 1950's, so predated the Redfields, as did the first Weaver variables. Zeiss and Kahles were making variables long before that.

But ALL of those scopes were first-focal-plane, which meant the reticle looked too thick at higher magnifications, especially for American shooters. B&L got around that withe the tapered reticle, while Weaver used a reticle with 3 parallel crosshairs, both horizontal and vertical. At low magnification the crosshairs tended to blend together, while at higher magnifications the center crosshairs were used for aiming.

Redfield was the first company to mass-produce a second-focal-plane variable with a constantly centered reticle and internal adjustments--exactly the sort of scope that shooters mostly use today.

Exactly how & where do I measure my rifles to get their scope height?

On low mounted scopes some riflemen have the tendancy to roll their head over the stock to align scope with eye. The opposite happens with a higher mounted scope. The rifleman lines up with the stock and sight picture without tilting the head to find the site picture.

Measure from the center of the bore to the center of the scope. Usually the top of the stock is right at the center of the bore.

Might find what you're looking for here:

http://www.24hourcampfire.com/newsletters/

I'd bookmark it.

I just picked up an Anschutz .22 with a Weaver V-8 (2-8X) scope with the triple wires as John mentions and external adjustments. Any comments on the scope as per value,collector interest, and years of manufacture, etc. I will be taking it off the rifle shortly as it is a little large and likely will sell it at some point.

I bought one off of eBay for $90.00 last year. I'm trying to get everything "period correct" on my Dad's pre-64 model 70 that I inherited.

I purchased the same model scope about fifteen years ago, as kind of a lark. Thought it might be fun to kill a deer with an antique scope.

By the time opening day was over, that scope had cost me four legal deer.

I finally figured out, that every time I pulled the rifle out of my saddle scabbard, I was laying my right thumb on top of the scope and moving it in the externally adjustable mount.

I put my trusty old 2.5-7x32 El Paso Weaver back on the rifle and killed a nice buck and a cow elk the next Saturday.

I am still looking for some person I dislike enough to give that old V8 to.

I discovered the same thing many moons ago but but my fix instead of higher scope rings was more drop in the stock.

Terry

Excuse me John but the article contains an error. This is not your fault because it is a common myth about the scope height. In reality the canting error does not depend on the scope height, only on the canting angle and the bullet drop at the given distance which can be proved very easily anyway.
Cheers, Andras

Andras,

I would appreciate your explanation of that easy proof.

My understanding of cant is that the higher the scope, the farther the bore lies from the vertical line of sight, given a certain angle of cant. The increased distance from the line of sight creates more error in the bullet's trajectory.

It will be interesting to hear why this isn't so.

I remember reading in RIFLE, I think, a while back about someone shooting one of JOC's rifles and commenting that the crosshair was in the upper right hand corner. While centered is nice it sure didn't keep him from harvesting game with an off center reticule.

Yeah, a centered isn't nearly as critical as some of us think.

That said, there's a big difference between crosshairs that ended up WAY over against the edge of the view, and those in the early Leupold Vari-X's, which wouldn't move very far off center.

Completely agree, I certainly wouldn't want to go back.

Antiquated rocket science. My 30+ year old Vari-X II's stumble through it...

Hi John,

I'll explain it with pleasure, this is why I've registered on this forum. I'm also a shooter anyway but with air rifles (Field Target).

The shots from a canted rifle will impact along an arch, and the displacement of the pellet impacts depends only on the angle of the canting and the pellet drop at that distance (relative to the bore line).

The height of the scope has nothing to do with this. Why? It's proven by tests by J. Hogema and can be proved theoretically, too: if you aim at a point, the bore line looks with 'd' above (d is the bullet drop) so the bullet which drops 'd' can hit the target. If you rotate the rifle but still looking at the target, the bore line will draw a circle around the target with this radius 'd' and the impact will be always with 'd' vertically below this circle, independently from the scope height.

For the very easy explanation, why scope height doesn't affect the canting error, please have a look at the picture below:



Simply imagine a rifle with more scopes mounted on it, one above the other. Each scope is zeroed at the given distance, each sight line looks at the same point, where the gun will shoot. If you cant the gun with an angle, you might aim through any of the scopes, lower or higher, they look to the same point, the gun underneath will be in the same position too, so the canting error will be the same. The canted shots move along a circle and the amount of displacement depends only on the pellet drop (d) and on the angle of canting (a). It doesn't matter how high your scope is, you always have to pay the same attention to avoid canting the rifle.

Best regards,
Andr�s

JB, read the 'proof'.

Another example as mentioned on another thread, 'Formula Heavy'.

All I can say is it's probably a good thing we can apply 'cant' to rifle sight's height,.......in a circle.

That theory may may true at the exact distance that bullet impact and point of aim coincide. Move the target closer or further away, and I suspect there will be error. I think that "Kentucky elevation" would be somewhat less effective, when scope cant is introduced.

Jeff

Yeah, now I'm going to have to run some more tests, since formulas don't pack it when writing for magazines!

On the other hand, it's probably worth at least one article....

I must have been really lucky all these years to hit anything without access to that chart!
Interesting,though.

Jeff,

Aim point and impact point always do coincide - assumed that the rifle is zeroed properly. It doesn't matter that you set the scope with clicks or use one of the mildots to aim for different distances, the LOS will always look at the target and the barrel will look always with 'd' above in order to hit the target ('d' is the bullet drop relative to the barrel at the given distance). It's quite logical, ain't it?

Anyway, I've tested it, too. With an air rifle a small scope mounted on 2.5 cm CTC and then with another scope with risers at 10 cm. Zeroed both times then rotated with 45 and then 90 degrees, the canting error was the same for both scope heights.

It's another interesting question that if you don't know the distance and under/overestimate it, the canting error can increase or decrease (related to the precisely zeroed rifle), or even be fully eliminated. It can even happen that your POI is tragically low but remains on the same place with any canting...

John,

This is a very good idea, please try it - with the same rifle&bullet of course - with a very low and very high mounted scope. Zero the scope in both cases and then rotate the rifle with 90 degrees. You will find that the canting error will be the very same (exactly the 'd' anyway to the side and down as well).

The only thing you shall be aware of is that the 'd' value has to be much bigger than your own inconsistency. If you shoot at 50 yds with a big bore rifle then you can't really use the results. Use a small bore rifle with low-powered bullets.

Yes I'm going to write an article about it to our FT forum because many people have this misbelief and I don't blame them because it seems to be very logical at first glance but facts are facts.

I'm looking forward to seeing your test results.

Well, now you've gone and dunnit, MM.
You can bet there will be at least one, perhaps two, shooters in Montana checking this out....
The arc-of-bullets phenomenon is well shown to anyone who cares to try it, which is why I mount everything I can as close to the bore as I can. AND put a level on.
The article itself is sort of an interesting flashback to one of Ken's articles about scope height and the fatter "point-blank" you get, a few extra yards -- but I've never been in quite the shooting where raising the scope would be a consistent benefit. I take clicks or hold over.

m_m

Interesting stuff! My curiosity is definitely piqued. Look forward to seeing what JB comes up with. If winter ever ends here, I'd like to try it out, as well. This sort of thing is way more interesting than the soap opera that this forum has turned into! Thanks for posting.

Jeff

I'm going to test it again sometimes with an air rifle (about 5 cm drop at 20 metres so the canting error is easy to see), fully documented etc., I'll let you know the results.

And I'm going to test it with a centerfire at 100 and 200 meters.

John,

This chart may help you out, I did this myself a few months ago...

Thanks very much, Kirk!

How much are you asking for reprinting rights?

Just remember to give me credit in the article as usual. I will get even in the gopher fields in a few weeks...

John, in the past you wrote an article about stock fit and in it you wrote about a .375 H&H that the stock was fitted to you so when you brought it up the rifle lined up like a shotgun for you. I've always heard & read to mount scopes as low as possible. Now my scopes are mounted so when I mount my rifles I'm looking through the scope instead of scrunching my cheek down on the comb to get a proper alignment.

Thanks to your info I have my scopes mounted so my rifles are more comfortable to shoot and can get on target faster.

Dave,

Thanks! Good to hear.

Thought you were only allowed to use finger paint? !

Jeff

To this point in the discussion, it seems everyone is talking about the first point at which the bullet crosses line of sight(LOS).
Zeroed at 25 yards is zeroed at 25 yards no matter what the orientation of the rifle is.

My question is, "How does the steeper downward angle (relative to the bore/trajectory, not the earth) of the higher scope affect the trajectory compared to LOS once it passes the first zero point?"

And that is the pertinent question.

Maestro mds, the Hogema paper you linked to _appears_ to indicate that the avg. radii of the circles found experimentally varies between Low LOS and High LOS. Is that correct (statistically significantly)?

Please have a look at this image from there:

It seems to me that the POI's are on the same circle with either scope height.

I have shot rifle canting tests already (air rifle, 21 meters) and I can tell you that there is much more wobble than usual because you can't shoulder the rifle correctly, this is the reason of the relative big size of the groups.

If you mark the grouping size for the 0 degree shots and allow at least the same grouping for the canted shots as well, you'll find that they almost all are on the circle within this tolerance.

Or please have a look at my last shots: http://www.szottesfold.co.uk/2012/02/canting-error-teszteles.html
Sorry it's in my mother language but the pictures speak for themselves. Or you can use Google Translator from Hungarian to English.

That test has been done only with one scope height, previously I calculated the 'd' drop value from velocity and real BC (scope height was NOT involved) and drew the circle with radius 'd' on the paper, the hits landed of course along the circle.

Excellent work and graphics, maestro.

Maestro you're quite a contortionist to fire your pellet rifle inverted! Nice job demonstrating your point.

Now that it's shown theoretically and experimentally that the point of impact with reference to the first line of sight crossing (near point zero) doesn't change with cant, we need to test what happens after the projectile passes that near point zero. In other words, leave the rifle sighted for 21 meters and then fire it at 40 or 50 meters (or whatever limit a reliable group size can be maintained) with two different scope heights and different cant angles.

I concur that there won't be any deflection as long as one is shooting at the range at which it is zeroed but my thoughts are that once we shoot past that range that there will be more lateral deflection on targets beyond the near point zero.

If scope height didn't matter then it wouldn't have to be considered in normal trajectory calculations. I just ran an example on my I-phone ballistic calculator ("Ballistic") using a bullet with a BC of .500 at a velocity of 3000 fps on a standard day. With a 50 yard zero and a sight height of 0.5" the drop at 500 yds would be 51.9". With a 50 yard zero and a sight height of 3.0" the drop at 500 yards would be 29.4.

Now, granted that trajectories aren't straight lines, but let's assume that a rifle with the above parameters (zeroed at 50 yards but aimed at a target at 500 yards) is fired on its side and the bullet path is viewed from straight above, I'm thinking the L-R difference at 500 yards would be at least 13" or the difference of the two figures in the above paragraph (51.9" -29.4").

What do you think?

That's my guess as well, but will run my own tests--with a very accurate .30-06.

Maestro, I was referring primarily to the paper you linked, in which the table indicates a different radius for the Low LOS circle vs the High LOS circle (assuming "r" indicates the radius of the circle, as opposed to something else). The drawings in that paper also visually show differing diameters, though I was struggling a little to reconcile what I thought I saw in the diagrams vs what I thought I read in the table.
Different radii would indicate that, as you show, sight height is of little consequence at short range (such as air rifle range), but it would become a huge problem at longer range (such as centerfire rifle range).
So, I appear to still need help making sure I'm reading the publication correctly.

I think that this nothing, 1.7 mm difference while the groups were 8-9 mm big...

The author came to the same conclusion, anyway: "As Table I shows, no statistically significant difference was found between the low and high LOS condition for any of the circle parameters."

I'll write a detailed explanation tomorrow about your questions but first please help me with an information:

If you zero your rifle at 100 yds and want to shoot at 200 yds, what do you do?
- adjust the turrets by certain clicks?
- hold over by certain mildots?
- hold over by certain inches?
I mean not only you personally but in general the big bore rifle shooters, which method(s) do you use in everyday's life?

Thank you

I normally use holdover if the target is beyond my point blank range. In other words if I know my target is at 200 yds and I know the drop from a 100 yd zero is 4", I'll holdover what I estimate to be 4".

On the other hand, I do use some holdover type reticles on some rifles (e.g.-Leupold's B&C).

Some good discussion here.

With my '06 shooting 180gr bullets (and similar cartridges) I use the 2-0-8-24 method. Those numbers represent the bullet's path at 100, 200, 300, and 400 yards. Then I use the relative size of the animal to estimate holdover. A deer is about 16 inches thick from top of shoulders to brisket (18 inches for a big one). With the bullet dropping 8 inches at 300 yards, put the horizontal crosswire on the top of the deer. At 400 yards I pull the crosswire above the shoulder about the thickness of the deer's body for a total holdover of 24 inches. I don't shoot beyond that at live animals. This system works for me.

Windage is the real blinger. I tend to overestimate wind speed. Ten mph is a harder blow than most people realize, I think. Even if we accurately measure wind speed where we are standing, that says little about the wind at the target and everywhere in between. Honestly, I don't have a system for estimating wind drift, and I'm open to suggestions.

The scope's height above the bore is meaningful as regards trajectory. The effect of canting of the scope or the rifle is dependent on the degree of cant and how it is handled.
If, for instance, the scope is 2 inches above the bore, the rifle is canted 45 degrees left, and the scope is mounted so that the crosshairs are vertical, the scope will be offset by roughly 1.1 inches and the effective height will be about 1.1 inches as well. If this offset is ignored and the rifle is sighted so that is hits point of aim at 100 yds, it will then hit 1.1 inches to the left at 200 and will continue to diverge at the rate until it would be roughly ten inches left at 1000 yds. If the rifle was sighted so that the bullet hit 1/1 inches to the right at 100 yds, it would travel parallel to the line of sight (laterally, that is)and would remain 1.1 inches to the right from then on.
Of course, 45 degrees of cant is an extreme example but serves to illustrate.
There are two reason for mounting scopes higher IMO. The first is to accomodate the scope (large bell, etc.). The second reason is because the stock is straight enough that it becomes awkward for the shooter to get his head down. The AR15 platform is an example of a high line-of-sight mandated by a very straight and high stock design. Many of the old schuetzen-style rifles are examples of low sighting planes mandating a stock with a lot of drop.
So, gunmakers are, as always trapped in a world of compromise. They can make straight stocks which help to manage muzzle jump and look pretty good while doing so but they will have to settle with a scope which is mounted a bit higher than they might like (awkward appearance. exposed to damage).
I personally think stocks should have a little more drop at the heel than has become popular and svope should be mounted low. I like monte carlo combs too. This may reflect my age more than it reflects any reality but there it is! GD

You may be right, although a 15 - 20% difference failing to be statistically significant suggests that the test is either not very repeatable, the rifle (or shooter) is not very repeatable, too little testing was done to give much confidence, or the confidence interval used in the analysis is ...very different... from what one might more routinely expect to use.

Greydog's illustration is the idea I was coming around to, about how rifle cant could become significant at range. Nevertheless, his illustration also indicates how _insignificant_ rifle cant is in practical, hunting applications.

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.

* * * * * * * * * * * * * * * * * * * * * *

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 :-)

My goodness. This reminds me why I don't shoot at big game that is farther than 400 yards or so. It is more like engineering than hunting. It is not a test of me and the animal but a demonstration of what can be done technically.

This is only pure mental play. As an enthusiastic shooter I like to understand how things work. As an engineer I would have said that let's use a bubble level against all kind of canting error and it's sorted for ever :-)

Breaking news: if you zero your rifle at a range and then shot to a _shorter_ range, holding under with a certain distance, the higher scope will be LESS sensitive to canting.

After all, my proposal is to use the most comfortable scope height and a bubble level :-)