Scope mounting height

by B.B. Pelletier

Before we dive into this subject, let me observe that last Friday’s posting about the most popular postings to this blog has, itself, become one of the most popular posts! It has over 30 comments already, which is a record for such a short time.

Now, to business. This subject was suggested by DOT, who says, “I’m interested in mounting a scope on a rifle. One thing that does not seem to have been widely discussed is mounting height. If we do not want to remove the iron sights, is it best to go with rings that mount the scope higher so that our line of sight through the scope clears the iron sights? If mounted high, are there concerns about accuracy? If we mount it low, is there a shadow that is seen looking through the scope?”

From 357 Owner
We got such a good answer that I’m printing it here. “Dot, the issue of scope height is pretty much moot unless the iron sights are particularly high, or close to the scope bell. If either are the case, go high. Ghosting has never been an issue with the rifles I have scoped, but I have also never had one with large, high, or obtrusive sights. Accuracy should not be too much of a factor as long as it is sighted for a good medium working range. Practice at ranges used, and adjustment comes easy after a bit. Don’t expect good results if you switch between 15 and 50 yards if you go for a high magnification. And don’t plan on using the iron sights if you scope [your rifle], as even with high mounts it is a pain to use them effectivly with any speed. Not enough sight picture, and I think it messes with a part of your head switching between glass and iron with any rapidity. I’ve done my time behind a bit of glass, and iron, and do both well. But not at the same time.” He said a lot there, but I would like to add my two cents.

For the CF-X guy
I gave a rather terse answer to the CF-X guy, who wants to scope his new CF-X with the lowest possible mounts. I have learned from experience, as 357 Owner also points out, that the height of the scope over the barrel really makes no difference to accuracy. The key, as he says, is to know your rifle and be familiar with it at the ranges you intend to shoot. Allow me to explain.

The “low-scope” crowd believes that, by getting the scope as close to the bore as possible, there will be less trajectory arc to deal with. This, they reason, makes for a flatter-shooting gun. In fact, it does not! Nothing you do with the sights makes one iota of difference to the drop of the pellet when it leaves the muzzle. The pellet begins dropping the moment it leaves the muzzle, and that drop increases rapidly as the pellet decelerates. Nothing optical can change that. The secret to a good air rifle sight picture is to select the optimum span of the trajectory within which the pellet arcs the least and gives what, essentially, looks like a zero that doesn’t change. In other words, sight in for the first zero point at 20 yards, and the second zero point will be anywhere from 27 to 37 yards, depending on muzzle velocity and the pellet used. Caliber makes no difference in this determination, except that .22 pellets are usually slower than .177 pellets. Read more about the best zero points for an air rifle scope in the posting At what range should you zero your scope? and the follow-on to that post, More about sighting in.

You need a scope level!
The higher you mount a scope, the more you need to check level before every shot. B-Square, makes a great one that keeps you on an even keel for every shot. I like this model because it sticks out to the side, where I can see it without taking my eye off the target. The levels that ride the scope cannot be seen unless you move your head, which defeats the purpose of a level. That said, there is no scope that is so low that there isn’t some possibility for canting error when sighting. You can struggle to mount your scope as low as possible, butyou’ll still need a scope level, unless you get the scope somehow looking straight through the barrel of your rifle!

Do the open sights obscure the target when you use a scope?
Absolutely not. You can even mount a laser on top of your rifle in front of the scope, and you’ll never know it’s there. One thing about that…any object in the line of sight reduces the amount of light that comes through the scope. If there’s too much stuff in the way, things can get dark!

A lower scope IS easier to see!
The new Leupold VX-L scope has a conformal cutout in the objective lens and bell to allow the lowest possible scope mounting. Leupold knows this doesn’t make any real difference for accuracy. They tout the scope for lowering the exit pupil to allow the best spot-weld on the comb, while allowing a large objective lens for the best light transmission. This is the only real advantage such a scope gives. Another solution is to modify your existing stock so it fits your face properly. If stockmakers ever wake up, they’ll start producing stocks that actually fit right to begin with. Most Theoben and Whiscombe rifles do, but they are the exceptions. This is a good reason to install an adjustable cheekpiece.


Leupold’s new VX-L scope allows the lowest possible mounting for the best stock spot-weld.

You don’t have to listen to me
Scope mounting is such a personal thing that you should do whatever suits you best. A lower scope is also no less accurate than a high one, so do what pleases you. After all, that’s what airgunning is all about!

38 Responses to “Scope mounting height”

  • Joe in MD Says:

    BKL mounts are highly favored by field target shooters and have a bubble level available. Most FT shooters will use the “high” mounts with a distance between the centerline of the barrel and the scope center of 1.5″ to 2″ although some go at least another 1/2″ higher. There is some minor (IMHO) advantage of higher mounts for longer shots but the problem occurs at close ranges (10 yards) when you may run out of clicks, have to turn the elevation more than one turn, etc. (Some people use a mildot scope and use a lower tic mark for their close aiming mark for this reason.)

    High mounts may also require some shimming of the mounts or buying mounts with built-in “shimming” (BKL and Mac1 can make custom mounts with the optimum angle for your gun/scope).

    For the ultimate in levels, get the electronic eyepiece level from Long Shot Products. They also sell a tool for aligning the scope, barrel, and reticle. The whole package is about $145.

  • DOT Says:

    B.B.,

    Thanks for clearing up some of my misconceptions. I thought the open sights would definitely be a problem with a scope, but it sounds like it won’t. And thanks too to 357 & joe for their comments. This place is great for getting some good info.

    Thanks again.

    DOT

  • Anonymous Says:

    BB,Please tell me the speed of the gamo cf-x with eujin 16.1grain pellets.I triyed the calculator but it said its 1000.05 wich is impossible.

    CF-X guy

  • B.B. Pelletier Says:

    CF-X guy,

    The calculator tells me 650-675. I haven’t chronographed it yet.

    B.B.

  • Anonymous Says:

    CFX Guy,

    649.69fps give or take

  • cold shooter Says:

    B.B.
    Please give us a source for Ballistol oil. thanks.

  • Anonymous Says:

    BB and anonymous,

    Thanks for the answer.BB I want to ask you, Can the eujin pellets (16.1} kill a racoon or some thing bigger?

    Are the accurate?
    Are they 100% lead?
    Are they worth it?

    CF-X guy

  • Anonymous Says:

    BB,

    Can you put a sling in the cf-x.If so, does pyramidair carry them?

    CF-X guy

  • Anonymous Says:

    BB,

    Can you mount a bipod in the gamo cf-x.I ask because its a underleveler.If so wich one?

    CF-X guy

    Sorry for so many questions : – }

  • B.B. Pelletier Says:

    cold shooter,

    Pyramyd Air is looking into carrying it. For now, however, I buy mine from http://www.midwayusa.com

    B.B.

  • B.B. Pelletier Says:

    CF-X guy,

    I haven’t tested the CF-X weith any pellets yet, so I don’t know how the Eun Jin pellets will work. Their weight is a bit heavy for a gun with the CF-X’s power. They would be better in a Talon or a Condor. The max weight for the CF-X is probably 11 grains or so.

    A bipod is going to be very difficult to mount on a CF-X because of the underlever. I know of none that will work. Maybe our readers know of something.

    You can put a sling on the CF-X but Pyramyd Air doesn’t carry the front mount that you need. It’s a half or three-quarter circle that will clip to the underlever and become the quick detachable base for a QD swivel. Look online (through Google) for sling swivels. You’ll find a source. The rear mount has to be screwed into the composite stock. I have no idea how a Gamo stock accepts wood screws or whether you have to use another method. Perhaps one of our readers can help?

    B.B.

  • Anonymous Says:

    BB,

    Can you try some eujin pellets with the cf-x and tell me if they work?

    I want them to go hunting without buying a .22 caL gun.And Im placing an order on pyramid air and if they work ill order a pack or two.

    CF-X guy

  • Anonymous Says:

    B.B.,
    I notice some of your readers seem to think this blog is a cure all. Whilst B.B.’s
    Blog is full of ideas and great infirmation it will NOT make you get accustomed with the way your rifle/pistol shoots. Only lots of practice with your gun will accomplish this! First hand expirience with your own equiptment(rifle and pellet combo), hands on is the only way to know for sure. Every gun is slightly different, even the same models with consecutive serial numbers. Before you ask BB, try to answer your questions about your gun/pellet performance on your own. You’ll be practicing, becoming more familar with your weapon and might even answer some of your questions along the way. PRACTICE WILL MAKE YOU A BETTER SHOOTER! Get out and SHOOT.
    Jason

  • B.B. Pelletier Says:

    Jason,

    May God bless you!

    B.B.

  • Anonymous Says:

    Good point, Jason. But I doubt that the majority of the traffic here is here for cure-alls, just advice. $1 a day isn’t much, but over time it adds up.
    To B.B. and Dot, you’re welcome and thank you for the recognition, I did not think I did such a good job, I left a lot out. But it was a long post already(sorry).
    Thanks again,
    357

  • Anonymous Says:

    I left a comment under the 350 magnum post but haven’t recieved an answer so I’ll put it here. I have a gamo 1250 in .22 and I have a leapers 4-16x 30mm 56mm objective with a one peice high mount on it, now I know that I should have used a lighter scope but I like it’s features, so my question is whats the BEST scope stop that will stop the slippage. the stop pin that came on the rifle bent back cause the main part of the stop is made of plastic. I’m looking at B-SQUARE’s scope stop on pyramyd airs website because the pin looks big but I don’t know if it will enter the holes on the 1250′s scope rail. please help. Thanks BOB

  • Brit visitor Says:

    The grubscrew stop-pin on Accushot mounts fits other Gamo rifles and seems very unlikely to yield.

    Found a use for the slip-stop that comes with Gamo rifles… with double mounts don’t put it behind the scope’s rear mount – just use the rear mount’s own stop-pin.
    Tighten the rear mount in place. Set the Gamo slip-stopper on the scope rail just behind the loosely fixed front mount. With luck the Gamo stop-pin can be located into one of the rifle’s scope-rail holes. Tighten up the Gamo slip-stop, then pull the forward scope-mount hard back against the nylon block on the Gamo unit, and tighten it in place.
    The scope is now effectively double-pinned.

  • B.B. Pelletier Says:

    Brit visitor,

    Thanks for that tip!

    B.B.

  • andreas Says:

    B.B.

    According to my drwings and calculations, a scope which is mounted high(er) will have its two intersection points later than a low mounted scope.

    I may be wrong about this, I am not sure…

    If you draw the pellet’s trajectory on a piece of paper and then draw two straight lines from two scopes (one high and one low) you can see that the accuracy is about the same, but the “good” interection points are later for the higher one. By “good” intersection points I mean resonable intesection points which are good for accuracy (eg 20-34)

    Also, you said that a pellet’s rate of decrease of hight becomes bigger as the pellet moves farther away. Which is absolutely logical.

    So, if the two intersection points of the high scope are farther/later, then it actually means that the arc will be move curved at that later stage of the pellet’s path.

    Which actually means slighly more accuracy. (?)

    BB, please correct me if I am wrong, that’s the way I think of it…

    You can try making that drawing yourself.

    Where do I go wrong?

    Thanks a lot.

  • B.B. Pelletier Says:

    Andreas,

    Stop drawing and start shooting. The two intersection points are determined by the location of the first one. Scope height has nothing to do with it. Scope height will affect the length between the first and second intersections, but it isn’t much.

    Get on the range and shoot your gun. You will see for a fact how it works.

    B.B.

  • andreas Says:

    That’s probably what I should do.

    So there is actually some difference between the two arcs. Well, as long as it’s a small difference it’s ok I guess.

    I just want to make sure about some things first before I start spending my money on rings and scope. I haven’t even received my rifle yet…

    Do you know if pyramydair can tell me about the fit of a scope on a specific rifle and what hight of mounts I need to get?

    I have a CFX and I ll be getting a leapers 3-9×40 5th gen. illuminated scope with AO.

    I ll be getting two separate adjustable rings, and I am wondering if I can get away with the low rings (for better eye allignment, not for the arc/accuracy matter) instead of the high ones.

    Can pyramydair check this? Do you know the correct hight?

    Thanks a lot for your kind help.

  • B.B. Pelletier Says:

    Andreas,

    Yes – call Pyramyd Air. They can check things foir you if you ask.

    As for mounting with low mounts, it won’t work because the receiver is straight. There is no clearance for the objective bell.

    As for not using high mounts, many shooters have a similar aversion. Yet in field target, where pinpoiunt accuracy is essential, everyone uses high mounts and one guiy I knew used a custom mount that was four inches high!

    The height of the scope doesn’t matter, as long as the scope is positioned correctly for you.

    B.B.

  • andreas Says:

    BB,

    Thanks for the info. I will go for the high mounts but I ll contact P.A. first.

    I have read most if not all of your articles on scope mounting. Have you written one about the B-square adjustables?

    Will I have a hard time setting them? They do come with a manual right…?

    I know I ask a lot of things, but I want to make sure, since shipping costs here from the US are crazy, and I can’t afford a mistake.

    Air gunning is one crazy hobby for sure! I am sure glad I found this blog.

    Thanks again

  • B.B. Pelletier Says:

    Andreas,

    Why are you buying adjustable rings? The CF-X works well with non-adjustable rings. At least it did in my test.

    Now I can do a posting about adjusting them, if you still want. But if you can get away without them, your mounting will be much simpler.

    B.B.

  • andreas Says:

    BB,

    I am buying adjustables so that I can get away with as less scope adjustment as possible so that I won’t get into the extrems and loose accuary. Isn’t this the point of having adjustables?

    I might be missing something.

    I remember that you used non-adjustables, but I thought you did it just for an easy set up, so you can test the rifle quickly.

    I just want to avoid the extreme settings of the scope windage and elevation. Are those dependant on the rifle itself?

    Also, BB, can you please tell me if all the b-square separate rings (not one piece) come with that stop/recoil blade/screw?

    Thanks

  • B.B. Pelletier Says:

    Andreas,

    Okay, go with adjustables.

    Read the specifications for each set of rings you intend purchasing. They will tell you if they have a stop pin. B-Square makes hundreds of models and I don’t know about all of them.

    B.B.

  • andreas Says:

    BB,
    Alright, so it’s called “vertical stop pin”.

    Hey, if the adjustables are overkill, I would gladly go for the fixed ones. It’s a $34 difference. Can I be sure that I won’t need them?

    I read your article on adjustables, but the only way for someone to know if he needs them or not is to test the scope on his rifle.

    So why not go with adjustables in the first place?

    Thanks
    Andreas

  • B.B. Pelletier Says:

    Andreas,

    If you think you want adjustable mounts, then get them. They are just as rugged as non-adjusting mounts, plus they leave you will all your scop’s internal adjustments.

    B.B.

  • Anonymous Says:

    Andreas,

    I realize that your concern is getting your CFX scoped and centered for adjustment as much as possible to leave your scope’s internal w/e unfettered, while at the same time doing so economically.
    Now, assuming that you are purchasing the CFX combo that comes with rings, scope stop, and 4×32 BSA scope, why not try the mount that comes with the combo first before you go out and get adjustable mounts?
    I would use the scope that comes with it as a check to see if it is difficult to get aligned, then switch over to the larger Leapers you mentioned to see if its objective bell clears the action once positioned in the rings.
    From what BB and others I have read mentioned, the fixed barrel is a huge advantage when it comes to scoping, as the stationary barrel is nearly as easy to get a scoped aligned with as it is with a bolt action centerfire rifle, quite unlike the situation with most break barrels that are afflicted with the notorious barrel droop that so confounds scope mounting.
    It seems likely that your scope will need only minimal adjustments to match the CFX bore.
    On the other hand, assuming that you are buying the CFX with neither rings nor scope, then it seems more sensible to go ahead and order the somewhat more expensive adjustable mounts to get something that will be more likely to give what you want the first time.
    Just with a cursory glance, it looks as if the B-Square 10101 is the way to go if you have a 1″ tube and want a two-piece mount, while the B-Square 17101 looks like the option if you want a one-piece mount.
    Both of the above mentioned mounts incorporate the vertical stop pin that seems to offer the best positive lockup, along with what I understand to be the absolute industry standard windage/elevation adjustments that don’t wreck scope tubes.
    That part in bold is essential, unless you REALLY want to take a chance with destroying that nice Leapers.
    I also have a CFX combo on it way from another vendor, while I have a Centerpoint 3-9×40 (1″ tube) non-illuminated scope on its way from Pyramyd.
    I intend to see if the mounts that come with it are a) tall enough to accomodate the larger objective bell of the Centerpoint, and b) if the scope aligns without having to make huge adjustments.
    I’ll probably go with one of those two B-Square mounting solutions if both criteria aren’t met.
    From the massive volume here and on other sites, it looks as if Gamo has come out with something remarkable in the CFX…at least I hope so.
    Oh, and one more thing in passing to those enquiring whether this pellet or that (especially the ultra-heavy Eun Jins) will produce decent accuracy with the CFX.
    You should know that no one projectile works perfectly in all guns, and that includes rimfires/centerfires.
    Hell, with centerfires, it is common for one bullet to shoot well in a given make and model rifle, but shoot poorly in the next consecutive serial numbered rifle of identical make/model.
    You don’t really know how well any pellet will perform in your CFX until you try it, but it looks likely that Beeman Kodiak or similarly heavy pellets don’t work well with the CFX.
    With centerfires, this usually indicates that the rifle being used has an overly slow rifling twist rate to stabilize heavy bullets.
    My Ruger M77 .30-06 shoots 5-shot 100 yard groups of 1″ with the “non-target” Sierra 180grain spitzer Pro-Hunters, while the Sierra 168 Matchkings won’t even do 2″, so you can see the flaws in calling one projectile or that the “best” when it comes to accuracy.
    Now, go shoot.

  • FMA Says:

    Hi, I’m very glad to have found this blog. I’m a Hungarian FT-shooter (so sorry about my bad English).

    Everything is O.K., but there’s a sentence what I can’t agree:
    “The higher you mount a scope, the more you need to check level before every shot.”

    So far I know, the mount hight doesn’t affect the canting error. The error depends only on the canting angle (with the same rifle and pellets and distance of corse), so you should always carefully check the level, with even extremely low mounts, too.

    The reason, shortly: when you zero a rifle at a distance and begin to shot aiming the same point but canting the rifle up to 90 degrees, the POI-s will show a half circle, where the radius is the distance between the bore line and the trajectory (bullet drop) at the given distance – the mount height doesn’t matter at all (even if many shooters do believe it :-)

  • B.B. Pelletier Says:

    FMA,

    Yes, the higher you mount a scope, the more any cant will thrown the pellet to the side. For example, if a scope is mounted 6 inches above the bore of the gun, any error from cant will be much greater than if the scope is mounted one inch above the bore.

    I have tested this at 50 yards with 6 independant shooters, all having scopes mounted at different heights, and we found that the higher scopes gave more of an error.

    If you aim a rifle with a six-inch high scope at a target 50 yards away, and then cant the rifle 90 degrees, you will be pointing the barrel at a different spot than if you just rotate the barrel of the rifle 90 degrees without moving the barrel. That would be like a scope with NO separation.

    B.B.

  • FMA Says:

    Hi BB,

    thanks for your answer. Maybe i’m thinking it wrong, but then you can sure say, where is my theory false:

    Fig. 1.

    1. If you shot with a gun, the bullet will drop (d). This points downwards and is a constant at the given distance, energy, pellet etc.. If the bore line hits the target somewhere, the POI will be under it on a vertical line, at a distance ‘d’.

    Fig. 3.

    3. The scope can be higher or lower, the bore angle will be other, but the bore line must point always to the same point, ‘d’ above the target.

    Fig. 4.

    4. So if you rotate the gun around the sight line, the bore line will draw a circle on the target paper around the target point, where the radius is ‘d’.

    Fig. 5.

    5. When canting, the bore line points at a point of this circle, and the POI is with ‘d’ under this point. The impact points draw an another circle.

    Fig. 6.

    6. See it in the practice. The Chairgun gave me the ‘d’ value at 17 meters for my airgun, I’ve drawn a circle with this radius, sighted in my rifle to 17 meters and shoot with every kind of canting. There was a little wind to left, but you can see that the POI-s follow the theoretically circle. And if you see in the Chairgun, when setting another scope height, the bullet drop (= the radius) will not change, so the canting error won’t change either.

    Or did I miss something?

  • B.B. Pelletier Says:

    FMA,

    It isn’t the bore that points at the target, it’s the sight. The bore is offset from the bore by the height of the sight above the bore. As long as that is directly above the bore, the offset is treated as an elevation issue. The moment the offset moves to either side of the bore through cant, then the bore starts pointing to one side of the target.

    That’s what happens, but try the experiment yourself. Cant your scope by a measurable amount at shoot a group at 50 yards or meters. You will see the offset yourself.

    B.B.

  • FMA Says:

    Hi BB,

    please see my pictures too, and read carefully what i’ve written, it’s not so difficoult, you will understand it just think it over…

    Or, if you don’t believe me, see this:
    http://home.wanadoo.nl/jhogema/skeetn/ballist/cantexp2/cantlos.htm

    I’ve made a test like this, too. I shoot with the same rifle, indoors, with a diopter (1″ high) and then with my FT-scope (4″ high). The result showed, that the moving of POI did not depend on the height of the sight line.

    It depends only on the canting angle and the bullet drop. And that gives the answer to your test’s results, too. You shooted wit different rifles, with different bullet drop values. And who makes generally his sight line higher? Right, whose drop is greater, because higher sights give better ballistic at greater distances. That’s the only reason, why was the canting error greater at the higher mounts.

  • B.B. Pelletier Says:

    FMA,

    It looks like it’s time for me to test this again!

    Thanks,

    B.B.

  • FMA Says:

    Hi BB,

    right, that will be the best. If you can do, use the same rifle with a normal scope mount and then with a pack of risers.

    But if you see this picture, you don’t need to do the test, it’s enough to make it theoretically :-)

    Imagine that a low and a high mounted scope are on the gun at the same time, above each other. Both are zeroed at the distance, both sight line point at the same point, where the gun will shoot.

    If you cant the gun, you might aim through the lower or the higher one, they point to the same point, the gun underneath will be in the same position too, so the POI’s canting error will be the same.

  • B.B. Pelletier Says:

    FMA,

    Now that explanation got to me! I understand your point!

    B.B.

  • Maestro Says:

    Hi folks,

    I've written a detailed article about high scopes and canting, with more test shot results and fully explained theory, if somebody's still interested in…

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

    András Fekete-Móró (FMA from 2007)

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