Effects of extra high mounts

I use high mounts to keep my neck up more than others. One thing you can do to keep your scope closer to optical/mechanical center is us a 20moa droop rail, or adjustable mounts. 

Also from your zero(25-30yds) to 50 yards you will have less holdover or fewer clicks so range estimation is a bit more forgiving. On the other hand your close targets, 10yds to 30yds there will be considerably more holdover points or clicks needed.

I have high rings on all my guns I shoot standing. During the years I shot small bore silhouette I found that high rings made for a much more comfortable head position. 


My field target gun also sports high rings. They seem to be fine shooting off sticks and for the forced standing lanes. I really haven’t noticed any issues with accuracy. I use StrelokPro to get close sight settings and have an accurate scope height entered in the program. The suggestions from the app are pretty close but since I always shoot all the distances when I set up my side wheel the programs accuracy is not as important because I make my own decisions about where my holdovers are. 


So to answer the question re issues. I don’t have any and don’t really even think about it. 


Corky

Just know that the higher the mount, the more effect CANT has on the POI.

FYI it is a common misconception that high mounts aggravate cant error.

Here’s a good article that seeks to clear it up. 

http://www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html

 

FYI it is a common misconception that high mounts aggravate cant error.

Here’s a good article that seeks to clear it up. 

http://www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html

Click to expand...

This is false because you take a narrow example and try to generalize it. The statement you make, and use the article to support, is ONLY accurate for one specific type of shooting-namely when you click to zero AND you know the exact distance at which you are shooting. In other words, the common field target method of shooting. Stating GENERALLY that "it is a common misconception that high mounts aggravate cant error" is simply wrong in that context. The statement is ONLY correct in the specific limited (but apparently commonly used) field target method of ranging and click to zero, and then ONLY IF the ranging is accurate. Even the writer of that article states as much himself.

IF one shoots only in the "field target" method of range and then click to zero AND can always range accurately then the statement is correct. That leaves a lot of other shooting situations where your statement IS NOT UNIVERSALLY ACCURATE.

No, it applies both for clicking and for holdover/holdunder points on the reticle...which for all practical purposes covers all of shooting.

These points are addressed very specifically in the author's summary at the end:

"In general, especially in FT shooting, where we do the required correction of LOS within our scope (i.e. adjusting turrets or holding over with certain mildots), the canting error is totally independent from the scope height, higher scopes are NOT more sensitive to canting angle than low ones."

Scotchmo, rsterne, and I all tried to explain this to you about a year and a half ago on GTA.

Quoting Scott, "When POA matches the intended POI, then scope height NEVER matters with regards to gun cant. Not even a slight difference."

You (and they) were wrong then and you are still wrong. Your general statement does not apply to holdover, only to click to zero.

Simple question to you. Assume two identical rifles with identical pellets. One has a scope 1" above bore and the other has a scope 3" above bore. Both are zeroed (near zero) at 20 yards. You have a target at what you think is 60 yards and you hold over the correct amount to hit the target (obviously a different amount of holdover for each setup but easily done). Then you cant each rifle the same amount while holding over the correct amount for each. Do you seriously believe that the observed cant error seen at the target (the amount the pellet moves laterally in relation to the target) will be the same?

Hang on, I want to keep score.

scotchmo: 0
rsterne: 0
nervoustrig: 0
András: 0
bandg: 1

Okay thanks!

Regarding the hypothetical scenario you described, yes if you canted each rifle at the same angle and used the proper holdover (which would be a different mildot for each rifle, as you correctly pointed out), the POI error would indeed be the same.

If instead we compared them using the same mildot (say, 3 mildots down on both rifles), their errors would differ but that would fall into the category of a ranging error...i.e. using the wrong mildot.

Anyone reading this who would like to actually understand it and who owns a rifle (or possibly pistol) that has open sights and also can have a scope mounted can try this for themselves. It really is simple geometry and the "field target" type guys or those who buy the Zottesfeld stuff just seem to have trouble grasping the concept. As the author of nervoustriggers beloved article notes, firearms shooters didn't agree with him, probably because they aren't always stuck in the "click to zero" frame of reference.

Try this-mount scope to rifle and zero at as close a distance as is reasonably possible. Lets say you can get in to 15 yards with scope mounted 2" above bore and zeroed. A higher mounted height illustrates the difference even better but 2" is probably a more common mounting height. Shoot, hit target. Now lay the rifle on it's left side (muzzle right of scope). This is extreme but it's the definition of CANTED, 90 degrees canted in this extreme example. Aim, shoot, hit maybe just a bit low (gravity and velocity will be the ONLY thing causing drop shooting this way) but in line vertically because it was zeroed at that distance (bore line converges with LOS at that distance). Now move the target out to 30 yards. Gun still on left side, shoot, hit a little more low (same gravity and velocity still at work) but now 2" left of target BECAUSE the muzzle is right of scope (LOS) 2" so the original zeroing (which hasn't changed) has the bore converging to line of sight at 15 yards (a relatively steep angle) and then the pellet continues moving progressively left as it gets out to the target now at 30 yards. It will hit 2" left. Simple geometry. If you continued out to 45 yards the leftward movement seen would be 4". Simple geometry.

Now take the scope off and do EXACTLY the same thing with open sights. Assume the sights are 1/2" above bore. Zero at the same 15 yards (common zero distance for both the scope and iron sights). Shoot, hit target. Lay rifle identically on it's left side. 90 degrees canted. Shoot, hit EXACTLY the same amount low as with the scope (it's only the same gravity and velocity causing drop) but in line vertically. In line vertically BECAUSE bore and sights converge to target at 15 yards, as it did with the scope, but this convergence is now at a MUCH SHALLOWER ANGLE than it was with the scope due to the LOWER SIGHT HEIGHT (open sights are much closer to bore). Now move the target out to the same 30 yards as you did with the scope. It will impact EXACTLY the same amount low as it did with the scope (only gravity and velocity at work in that plane) but now hits 1/2" left of vertical. It started 1/2" right of vertical because it's on it's side but moves left at a shallower angle than above, crosses the vertical at 15 yard zero distance, and moves gradually further left (but MORE SLOWLY than the scope shooting because of the shallower angle) to hit 1/2" left. Continue out to 45 yards as above and you will see impact at 1" left. Simple geometry.

Anyone who wants to try this will see how it works. It's simple geometry. The longer the distance the higher the ballistic arc must be inclined to reach the target (think holdover). But at the same time the longer the distance the more progressively the impact will move laterally for a higher mounted sight in relation to a lower mounted sight for ANY given degree of cant IF the two are zeroed at the same near distance. This isn't a "ranging error". It is simple geometry at work for different methods of shooting. Only if one clicks to an accurately ranged distance will the cant error be the same for the two sight heights. If using holdover, the error will be greater for the higher mounted sight. The amount of holdover necessary isn't the critical part of the process, it is the difference in horizontal ANGLE that results from canting two different sight heights that is most important.

Again, it's not limited to clicking. When using mildots as aim points, you have effectively re-zeroed the scope for the new distance. In other words, the pellet will land on the zero (say, 2 dots down) provided the reticle is held true to the force of gravity.

Put simply, as long as the line-of-sight compensation is done within the scope, scope height does not matter. Only the angle and gravity (amount of drop) matter.

It's only when the compensation is done at the target (outside the scope) that scope height matters...for example when hunting, aiming at the head in order to hit the body. That is, going for a vitals shot on a squirrel at long distance by centering the crosshairs on its head and expecting the pellet to drop some distance and hit it in the chest. You will get a different result with a high scope vs a low scope because the shot is being taken without a proper aim point (mildot)...an aim point that would be known and characterized for a given scope height.

A similarly contentious discussion was held here on AGN a while back in which one member took a hard stance backed up with mathematical proof, and then conducted an experiment and discovered what Scott said is correct. While I don't hold out a lot of hope that you will come around, I am hopeful it will help others who may be reading along and have the appetite for a deeper understanding.

https://www.airgunnation.com/topic/buble-level-anti-cant-device

Anyone reading this who would like to actually understand it and who owns a rifle (or possibly pistol) that has open sights and also can have a scope mounted can try this for themselves. It really is simple geometry...

Click to expand...

...15 yards with scope mounted 2" above bore and zeroed...lay the rifle on it's left side... just a bit low...move the target out to 30 yards...now 2" left of target...

You are describing a ranging error, where your POA does not match your intended POI. Aiming for 15yards when target is at 30yards. That is not the cant error.

...Assume the sights are 1/2" above bore. Zero at the same 15 yards...Lay rifle identically on it's left side....move the target out to the same 30 yards...now hits 1/2" left of vertical...

Again, you are describing a ranging error, where your POA does not match your intended POI. Aiming for 15yards when target is at 30yards. That is not the cant error.

As you said for the open sight example:
"It will impact EXACTLY the same amount low as it did with the scope"

Since the gun is on it's side, that is the cant error "EXACTLY the same", so the 2" scope height had the same cant error as the 1/2" high open sight.

When a gun is on it's side, the horizontal (with respect to gun) cant error exactly equals the projectile drop at the target distance.

horizontal shift = drop x sin(angle)

vertical shift = drop x (1-cos(angle))

I, too, am running into the problem the O.P. describes. I have a new AF Texan carbine. I bought a Hawke Match Mount 1 piece "high" mount for my scope. But with the way the Texan is constructed, when I shoulder it and plant my cheek I am eye level with the top edge of the scope. I then have to cant my head to the side to get my eye in line. Therefore, I need to find a way to mount it higher, especially as I am going to be using the gun to stalk hogs in the swamp where "shoulder-and-shoot" will be the norm rather than the exception. (Forget even thinking about stopping to make calculations)

So my question on this topic is the practical v. the technical. If a person mounts their scope high, then practices and learns how much it drops past the range they zeroed in at, does any of the technical aspect really make a difference in a hunting situation as described above, or is it more of a concern for the competition shooter going for hyper-accuracy. (After all, a 300 grain hollowpoint kills a pig just as dead slamming through both lungs 2" from your aim point as it does slamming through both lungs right on your aim point,)

So my question on this topic is the practical v. the technical. If a person mounts their scope high, then practices and learns how much it drops past the range they zeroed in at, does any of the technical aspect really make a difference in a hunting situation as described above, or is it more of a concern for the competition shooter going for hyper-accuracy. (After all, a 300 grain hollowpoint kills a pig just as dead slamming through both lungs 2" from your aim point as it does slamming through both lungs right on your aim point,)

Click to expand...

You are describing a rifles accuracy and how well it's being shot. Cant error is only a part of that. If when killing another creature you shoot for good enough an airgun may not be for you.

John can we get some pics of that Thomas from each side in full please

You are describing a rifles accuracy and how well it's being shot. Cant error is only a part of that. If when killing another creature you shoot for good enough an airgun may not be for you.

Click to expand...

LOL - really?! Well, I hate to break it to you but "a rifles accuracy and how well it is being shot" is what puts meat on the table and helps eradicate an invasive species doing irreparable damage to local flora and fauna, as well as the putting holes in your little paper target. The implication that I am an unethical hunter shooting for "good enough" and should therefore not be in the sport is both insulting and presumptive. You don't know me, bub. You don't know what shots I take, and which ones I pass up. To presume you do merely displays a level or arrogance most frown upon and I, myself, have no tolerance for.

Further, to suggest that an impact 2" away from intended target in a hunting situation is somehow a bad shot is laughable and suggests that you know little to nothing about the topic you are attempting to piously lecture me on. A hog or deer is not one of your little paper targets affixed firmly in place at a measured distance. They move, for one, often just as you take the shot. When you finally beat his nose to stalk up into range, the procedure is "shoulder-aim-fire", not stop and set up a bench and chair, pull out a sled and vice to help you keep your gun still, lase the target to within a millimeter (oops he moved, start over), measure humidity, barometric pressure and wind speed, go into your ballistic calculator and compute your shot, adjust elevation and windage on your scope accordingly, now line up on your....oh wait, your target is now a half mile away through the swamp and still going. Better luck next time. Maybe you could drug it to get it to stand still.

There was actually a question in there that you could have answered had you not chosen the rout of personal attack instead and it goes back to the O.P's question. In it, he mentions "shouldering" his gun and the scope not naturally falling in line with his eye. This is something you NEED in hunting (the whole your-target-is-moving thing), and may require you to mount the scope higher. But this might cause a slight shift in point of aim that changes with distance (?). But is this enough to override the benefits of having your rifle come smoothly and naturally to your shoulder, and the scope into your line of site without further contortions being necessary, as to make those high rings inadvisable, even in a more practical application such as hunting v target?

See, you could have answered that question.

I'd love to get back to the shooting issues (and leave the personal ones for PM's if so inclined).  

I like visiting friendly forums with friendly people — who might disagree — yet in friendly ways.  



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As a relatively new AG shooter — with limited powder burner (PB) experience decades ago — I found that I had very few PB habits to kick when getting into AG.



I could be totally wrong, but.... — here goes what I'm thinking:

(1) If we have had extensive PB experience, we have been taught (by our dad, or the pain that recoil gave us) to put the buttstock of the rifle into the soft tissue of our shoulder.

That buttstock location has become second nature (PB nature, to be exact).



(2) Now if we're shooting AG we don't have to protect us against recoil. But the PB habit is there, so when we raise an AG bullpup and place the buttstock onto the same shoulder spot we are used to put our PB buttstock — well, the scope will seem way too low....



(3) However, if we simply took the AG bullpup, raised it first to our cheek, found a cheeck weld that lined our eye up with the scope...

and THEN placed the buttstock wherever that might feel comfortable with the cheek, eye, and scope already aligned... 

we might find that we really won't need such a high scope. ➔ Just a different place to put the buttstock on our shoulder....



(4) Looking how EDgun, Tapian, Zbroia, Huben, and some others shape the buttstocks of their bullpups seems to be in line with this thinking (pic below). They could be rested half way on the top of the shoulder if that provides the most comfortable position for the head-eye-scope combination.





Just thoughts, in the end you'll need to decide what changes you're willing to make: scope height or butt stock placement.



Matthias

Hi folks, I would like to express some thoughts on the matter: So if you would have a boresight (scope hight 0) you would shoot low according to the trajectory of the bullet. Now cant the barrel 90 degrees. then poi would be the same, ie: no cant error. So to keep it short : scopehight does matter. because cant error starts as soon you have an aiming device. (iron or scope) in order to hit your poa, you have to point the barrel up (slightly) to compensate for G, wich leaves an angle between LOS and boresight. So if you cant 90 degrees to the left, you will shoot left and low, because instead of "up", your bore is now pointing left. the higher the scopehight, the bigger the angle and therefor more cant error. It's just my simple-man's train of thought and a very interresting discussion!