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Why do you need a scope level?

by B.B. Pelletier

I’m writing this report because I saw from the comments on the accuracy versus velocity test that several readers do not know what a scope level does. And where three people speak out, there are three hundred who are reading and remaining silent.

They say that there’s nothing more zealous than a convert, and I expect that is true of me when it comes to scope levels. I have understood their need for a long time and even conducted a fairly extensive cant test back in my Airgun Letter days, but it was my .38-55 Ballard single-shot rifle that really drove the message home. That rifle came with a bubble level, and it’s far more precise than the levels we find on air rifles today. The bubble moves very slowly, making it important to check the level just before you begin the squeeze; because what looks like a level gun one moment can change slowly to a canted gun if you don’t watch the level. By contrast, the scope levels I’m using with airguns have bubbles that move very fast, are much easier to see and are far simpler to work with.

Today, I want to demonstrate the effects of using a bubble level. I’ll use the same Whiscombe JW75 that I’ve been using for the velocity versus accuracy test, because we already know it has an accurate pellet in the Beeman Kodiak. For this test, I first seasoned the bore with six shots, then fired a group of pellets with the bubble deliberately off-center in both directions. I fired a second group where I paid no attention to the level and just tried to level the rifle as best I could through the scope. The final group was shot using the level with the gun absolutely level for each shot. The distance was 25 yards, which several readers mentioned is almost too close to see the effects of using a level.

This is the insidious part of leveling a gun, and it’s what I’m showing with today’s test. You really can’t see a pattern to the group from not leveling the gun when you’re shooting as close as 25 yards, but you can see that there’s a difference between a level gun and one that’s not level. We’ll get to that in a moment.

What the level does
The scope is mounted above the barrel, so it’s adjusted to look through the trajectory of the pellet so that the point of impact coincides with the aim point at a certain distance from the gun. However, if you tip the gun to either side and then sight it, your crosshairs will still be on the point of aim, but the barrel will no longer be directly below the scope. It will be to one side or the other, depending on which way the rifle leans.

Our intrepid blog reader duskwight was kind enough to give us a link to a superb animation of this phenomenon. You will find it here. Someone (Wulfraed?) said that a gun will describe an arced impact point if the cant is shifted through an arc, left to right. That’s exactly what the online animation shows, and it’s exactly what a scope level does for you.

One reader asked if the scope level would still make a difference if the scope had been optically centered. Yes, it would. There’s no relationship between optically centering a scope and using a scope level. The former simply allows you to adjust the elevation for different ranges without the shot group moving from side to side because the scope stays centered all the time, while the latter relates to how the scope and rifle are actually held when fired. The first is optical, and the second is physical.

The test
The test is straightforward. First, I seasoned the bore with several shots. Then, I fired a group of 10 shots at 25 yards with the rifle canted to the right for 5 shots and to the left for 5 shots. The cant was controlled by the position of the bubble in the level, and I stopped tilting the rifle the moment the bubble came to the end of its travel. Obviously, there’s some error in this, as the bubble level is not a precision instrument, but I think you’ll get the idea.

The rifle was titled until the bubble came to the end of its travel on the left side, as shown above. Five shots were fired at the target with the crosshairs on the center of the bull at 25 yards.

The rifle was then tilted in the other direction until the bubble came to a stop on the right side, as shown above. Five more shots were fired at the same target, just as before.

And here’s the group. Do you see that you cannot tell that the rifle has been purposely canted in two different directions? This just looks like a large group for a Whiscombe at 25 yards. Group measures 0.905 inches between centers.

Next, I shot another group of 10, only this time I completely disregarded the level. I just shot and tried to hold the gun level from the visual cues seen through the scope. This is the same way I shot the rifle during the initial accuracy test.

For this group of ten Kodiaks I disregarded the level. I tried to keep the rifle level by visual cues through the scope, but that was all. Group measures 0.874 inches between centers — or not much better than when I was purposely canting the rifle in two different directions. Also note how much like the first group this one looks.

For the last group I leveled the rifle for each shot. I was also careful to hold the rifle exactly like I was holding it for the other two groups. The results are very telling.

This group of 10 Kodiaks was shot with the rifle leveled each time. It measured 0.624 inches across the centers; however, if the stray ninth shot is omitted, it would measure 0.36 inches. If you check the last accuracy test I did with Kodiaks on Friday, you’ll see that this result is very close.

I’ve seen this same test result repeated numerous times over the years, so I don’t feel the need to run multiple groups and do a sample of each type, but you’re free to do so. I know this is what happens when a scope level is used, which is why I used one when I competed in field target.

You might ask why I don’t always use a level when testing airguns. The short answer: time. It takes a lot longer to settle down and check everything when you shoot this way, and I don’t think it’s always necessary, anymore than I would use a minute-of-angle rifle in a firefight. An AR 15/M16 is fine for that kind of work. But when real accuracy is on the line, a level brings out the very best a rifle has to offer.

45 thoughts on “Why do you need a scope level?”

  1. Yes, I think it was me…

    Though I was describing the path a laser boresighter beam would traverse presuming the scope where actually zeroed at the range rather than the preset boresight point.

    I think this is a test wherein having the scope/gun truly sighted in on the bull — rather than accepting “near the bull” groups — might have had some significance; especially if rerun at a longer distance, so the side drops would be more noticeable. Your final group was “up 6, left 4” (using the numbered rings for coordinates). OR — WAIT a minute: your target markings are upside down — did you shoot them with the target upside down?

    If not, and only processed the dime photos upside down… And counting the center as 10 using “10-x” to get coords…

    Final: right 6, down 4
    Canted (using an arbitrary split): right 8, down 7 AND right 3, down 5
    “Normal”: right 5, down 4.5

    (Regarding using the environment — were the numbers visible in the scope, and could you have aligned the cross-hairs on the lines of the numbers?)

  2. Morning B.B.,

    I am have a level attached to the Talon SS as far forward as possible. It’s easy, with some practice to shift from my right eye on the cross hairs to my left eye and the level.

    The Benjamin Discovery wears a scope with a bubble inside it. Real easy to shift from the bubble and the cross hairs.

    Just a reminder to everyone, don’t forget to use a level on the gun and the scope to insure that the scope is leveled to the gun. I had surprise or two when I actually checked what I thought were leveled scopes.


    • This is a PS on my post. I like to use the bubble level, bought from PA of course, to take out the variable of canting. When I miss, happens a lot, I like to know why so that I can improve my merger shooting skills.


  3. BB
    Could you possibly discuss a couple of available models of levels and their advantages? I am not convinced of the usefulness of the scope-mounted levels and, so far, I have only found the B-square level to attach directly to the action


    • TE,

      Yes I can do that if there seems to be enough interest, but here is the lowdown. The level needs to be set so you can see it while sighting through the scope. I sight with my right eye, so having the level set off to the left makes it easy to see with my left eye.

      What doesn’t work for me is any level, including the electronic ones, that are above the scope.


  4. B.B.

    I can see that canting problems (variable cant) with the scope not zeroed (particularly the horizontal plane) is going to cause a less conspicuous effect on the target than what the results would look like if the scope were zeroed or at least centered on the horizontal.

    What you have is what looks like a ratty group without an obvious clue that canting is involved. If the horizontal had been centered, the canted group would look more like a bent horizontal string. A frown of sorts.

    If you had been shooting a lot farther without adjusting the scope, the effects should have been more obvious.

    Wait… I don’t remember if you are using a scope or not. Does not matter much except that the higher the sights, the more effect that canting will have…..particularly at a distance not zeroed with the sights.


    • twotalon,

      Not really. I have done this many times before and where the scope is sighted to hit doesn’t matter. The gun performs the same — just in a different place.

      You are correct about the height of the scope. It does affect the size of the arc described when the rifle is canted.


  5. B.B.

    This is OT for today’s topic, but I need a clarification regarding the S&W 78G and 79G airguns. I was reading your different articles on them and noticed a discrepancy. As I’m currently on the hunt for just the right 79G, I need your clarification.

    In your July 3, 2009 blog you wrote, “The early guns . . . were finished matte black. Later guns had a shiny black paint. ” However, in your September 6, 2010 blog you wrote, “The first version of the gun was finished in shiny black paint . . . later . . . the paint was changed to a dull matte finish that was more uniform than the shiny black.”

    I know I want an early 79G with the two power levels and the adjustable trigger, but many on-line sellers, believe it or not, are unable two answer whether their specimen does or does not have those traits, and usually the important things are not visible in their photos.

    Help, which is earlier, shiny or dull?



  6. I’m hoping for big things here…ordered a scope level last Thursday from BKL. Unfortunately shipping to Canada is in the neighborhood of two weeks for little bits like this. Considering today the thermometer was a few degrees below freezing when I got up, with snow reported about 40mi west…whether I’ll really get to try the level before spring is somewhat iffy.
    I do know that this weekend I took out my netbook with Chairgun and tried extending my shooting to 50m with the Slavia.
    There was about a 10-15mph wind blowing…so not ideal for this test. Chairgun gave me a 10″ holdover and about 2.5″ windage.
    First shot about an inch off the bull at about 10 o’clock. Since I just wanted to see if it would group I didn’t change anything and fired 9 more shots.
    Got a group just a bit under 2″. Sitting with the front supported. Considering the wind, the power of the gun and the fact that it is a springer I was quiet impressed for a first time try.
    By-the-way anyone else see the Crosman M417 just announced by Pyraymd?
    My boys saw it this morning and have been telling me the last hour that this is a Christmas priority 😉

  7. So, there it is.
    Pusher slots being cut http://i53.tinypic.com/11tvtlg.jpg Lots of sound, lots of metal flakes, lots of smoke from oil used to cool the metal. The main pipe is just turned, not yet sanded or polished, main coupling installed.
    Job done for today: pins hammered into pin holes with green loctite, excess metal machined down, some rough deburring, two flat grounds milled in rear end http://i54.tinypic.com/55qxaf.jpg
    Next weekend will be a drilling day I suppose: crosspins for cylinder end plugs, trigger/cocking assembly and safety. And LOTS of sanding, deburring and polishing.


        • duskwight,

          I don’t know about that. As the owner of the world’s only Duscomb, I think you have something very unique. I have only know of one other case where a man made his own spring rifle, and that one was just a conventional breakbarrel.

          I reckon you’ll go in the Hall of Fame for this one.


  8. I’d say there is no argument that a scope level improves accuracy because of the physics that has been discussed. My reservations have to do with how it is actually used. David Tubb has a level attached to his front sight, I think. So, his shooting process has him using his left eye to check the level while his right eye is aligning the sights. Makes my head hurt just to think about. But maybe one gets used to it. Apparently, the pilots of Apache helicopters need to use their eyes separately to track all the data in their cockpits. They have splitting headaches for the first year, and then they adjust. The wife of one pilot says that she saw her husband seeming to use his eyes separately in a way that grossed her out. So she asked him if he could read the opposite pages of a book at the same time–one eye on each page–and he could…

    Special thanks to FrankB. Thanks to a special strop that he made for me and his patient coaching, my knives now positively slide through foodstuffs, and I am shaving hair off my forearms. I wouldn’t exactly shave with these knives, but I believe the threshold has been crossed, and I am intoxicated.

    B.B., yes, please tell us about your initial plans for the blog. As I consider the art of goal setting and decision-making, the rational approach comes to mind. As Thoreau said, “In the end, you only hit what you aim at, so you had better aim high.” No doubt that is true to an extent. But there is a huge discrepancy between the human intellect and the vast complexity that is out there, so could it be that the rational plan-making part of the mind could be limiting–in the same way that it limits the Jaws of the Subconscious in shooting? What then is the alternative? It would be too much (for me anyway) to attempt a wholly zen approach: “Don’t do something. Sit down.” The game would be to put your effort to some reasonable goal leaving enough flexibility to take advantage of what might come up. I’ll be interested to hear of the original plan of the blog.

    Wulfraed, were you in the Repo business too? 🙂 Not wishing to be credulous, I certainly believe that the Lizard Lick videos are heavily edited and may even by reenactments of various episodes, but I’m holding out for some truth content in there. The fighting techniques are crude and of no interest. But the real skill of the Lizard Lick “agents” is how they surf the landscape of word and action in a very artful way. Some of their putdowns are fairly ingenious. In one show an enormous woman throws two women out the door and as they walk of in disarray, shouting and cursing, the large woman says, “Go out and earn some nickels and dimes”…? Of more interest though is the obvious conclusion that while people can get very upset, very few truly want to fight. They will yell, curse, insult, shove, brandish weapons, including guns, and in one case a flamethrower and a grenade, but they never quite take the final step of engaging. If I’d been carrying a gun, I would have pulled it in many of those situations, but as it turned out, there was no need. In fact, the real element of mastery of Lizard Lick is knowing just how to surf the edge of disaster. In one telling instance, two enormous guys stand belly to belly with their faces inches away shouting, “Go ahead, swing!” And the other guy says, “You swing!” Nobody swings. Of course, sometimes they get stomped but even then it is no worse than what your average football player endures in a game.

    Immersing myself in Lizard Lick videos this weekend, I went from incredulity, to horrified fascination, to…envy??? Let’s think about this. Given that all we can count on is the day that we have, these guys have all the elements one needs. They’re sort of like primitive man. There is excitement and challenge and even a nice-looking receptionist–who is not a pushover by any means and has a background in powerlifting. At the end of the day, I like to think back on my rc flying and the targets that I’ve shot. These guys can think of swinging a bat at someone and saying, “I will send you like Babe Ruth. I will put you in left field!”

    Slinging Lead, there are women competition shooters out there who are really hot–Julie Golob of Team Smith and Wesson for example or Jessie Abatte or Tori Nonaka of Team Glock. Where they might give up some looks to Crystal Ackley, they certainly come on strong with their shooting. Or maybe the hotness factor comes from women dressed in snug shooting attire, loaded down with extra magazines and dropping a whole row of steel plates in a matter of seconds. Is it not true that women are much more heavily represented in the pistol competitions as opposed to the rifle? Maybe I should change my emphasis.


    • No… just 30 years as a software engineer.

      I have seen a few episodes of a UK repossession show during TDYs; and do have some understanding of law with regards to loans essentially secured by the item the loan was used to purchase.

    • matt,
      You’re leaving out the one important element that eliminates any credibility to a reality show – there is a camera in their face. Taking your example: Two guys belly to belly yelling at each other to swing first…with a camera in their face…what would you do?????? Most of the idiots ham it up thinking they sound cool for the camera.

    • Not having a TV, I only get to watch very occasionally, and then it’s usually in some place that just has the news on.

      A few months ago I stayed in a hotel a couple of days and I was amazed at the new TV fare these days. Lots of pawn shop shows like “pawn stars” and tons of shows devoted to having one’s things repossessed. The most amazing one has people coming to repo a car, but if the person/family can get 2 out of 3 questions right, they get to keep it (the company filming the show pays it off or at least pays it up to current, I think they pay it off).

      Amazing to see what this country has become and this thing is only just getting started.

  9. BB, a method I use when shooting paper is to level my cross hairs with something that is level or plum like the target board, post, or fence. That is a very quick way to stay level and consistent.

    David Enoch

  10. I am sure keeping the rifle level helps, maybe why target rifles usually have a wide flat forend.

    Off topic.
    My acid test for accuracy is being able to hit the actual number “3” all four times on a Gamo target at just shy of 14 yards.
    (all my basement allows)
    After that I take it outside and depending on the power the rifle it needs to keep a handful of shots in about a half inch “kill zone” at 30 to 45 yards.

    Anyone else use something other than groups (I just do that when sighting in a scope \ peep) to test a rifles worthiness?

  11. BB,
    That is an excellent demonstration of what difference level makes. Even without an actual bubble level, paying attention to level in some way makes a big difference. I’m still working on that with fixed sights and multiple ranges, and probably always will be :).

  12. I shoot at all kinds of things.
    Ornamental crab apples, paint balls, twigs, walnuts, pieces of gravel on top of my target stand, weeds, empty .22 brass, pellets……..anything I can think of. I have a huge jug of cheese balls that I was going to use, but I have been eating them instead. Maybe if they get stale.


  13. B.B.,

    Using “other queues” is a big help, and often the most practical way to achieve consistency when using a scope. The trick, as I’m sure you know, is to use the cross-hairs relative to things on your targets, like edges of the paper, or other bulls. What matters is that the shooter is conscious about cant.

    My small-bore rifles had a level that inserted into the Anschutz front sight, so it was visible from the real sight through the aperture. So it wasn’t necessary to use the left eye along with the right eye. This might answer Matt61’s question about what David Tubb’s did. I doubt that Mr. Tubb’s used his left eye.


  14. Is this canting worth worrying about when using a peep sight? It’s much closer to the bore than a scope, but I would think there is still some factor involved for the precision required for 10m target. Also, I don’t see any way to do any meaningful relative alignment with the small peep like you mention for the scope cross hairs. Seems like a level would be necessary for 10m but is it legal?

    • Lones Wigger in his glory days used to cant like CRAZY. Modern 10m shooters seem to not cant much at all. The standing position seems to have changed, from one with a twist like Lones used to use, to a less-twisty, “leaning up against a fence” sort of position and the rifles non-canted. I’m thinking the positions have changed and this has something to do with the higher scores since the 1970s, and besides it complicates adjusting your sights.

      I don’t think levels are legal in 10m. I have a feeling the latest UIT (or whatever they’re calling themselves these days) rules are online.

      • Flobert,

        The twist that Lones Wigger, and many others used, is actually the best way to shoot offhand, IF you are attempting to optimize the use, or effect, of muscle. There is an optimum amount of muscle stretch that steadies the position. This is not why “modern” shooters no longer use such a position. The reason modern shooters are more upright is because of the new super stiff jackets. During the 70’s, the rules for international competition were very different from what you see today. Back then, you’re shooting jacket had to be very thin, very loose, and could not be stiff. Back then, a gauge was applied to your jackets material at several places. In addition to this, during evaluation you would have to wear everything that you were going to wear on the line during competition, along with your jacket, and they would drop a kneeling roll down your collar, and the it would have to drop right through. Try doing that with a “modern” shooting jacket. Today’s jackets, and pants, and even underwear, provide so much support, that you can’t hardly move in them. It’s not that you don’t need to stretch the way that Lones Wigger did, you CAN’T stretch, even if you wanted to.

        To compare scores of today’s shooters with those of Lones Wigger, Dave Kimes, or Lanny Basham, is like comparing grapes and walnuts. It use to be that what distinguished international shooting from NRA was that in international shooting, the shooters performance reflected raw talent and ability, as opposed to equipment and binding or restrictive clothing. These days, there’s much less of a difference between the two types of competition.

        Also, with regards to 10M air-rifle, back in the 70’s, precision class air-rifles conformed to the same physical specifications as the “Standard Rifle”. Back then, air-rifles were not augmented in any way. You didn’t see the kinds of adjustable butt-plates, grips, or sight risers that you see today. Modern 10M air-rifles are much more like free-rifles in every way, except for the fact that you can’t use a hook butt-plane. That’s another reason why you’ll see 10M competitors appear to use better form. The rifles are now augmented to conform to each individuals unique body type.


      • Flobert,

        The twist that Lones Wigger, and many others used, is actually the best way to shoot offhand, IF you are attempting to optimize the use, or effect, of muscle. There is an optimum amount of muscle stretch that steadies the position. This is not why “modern” shooters no longer use such a position. The reason modern shooters are more upright is because of the new super stiff jackets. During the 70’s, the rules for international competition were very different from what you see today. Back then, you’re shooting jacket had to be very thin, very loose, and could not be stiff. Back then, a gauge was applied to your jackets material at several places. In addition to this, during evaluation you would have to wear everything that you were going to wear on the line during competition, along with your jacket, and they would drop a kneeling roll down your collar, and the it would have to drop right through. Try doing that with a “modern” shooting jacket. Today’s jackets, and pants, and even underwear, provide so much support, that you can’t hardly move in them. It’s not that you don’t need to stretch the way that Lones Wigger did, you CAN’T stretch, even if you wanted to.


  15. When out in the field, don’t forget the benefit of referencing all of nature’s “levels” that are available to you. Most tree trunks are a pretty good check through your scope against the reticle. Just be sure to mentaly average out both sides of the trees, or work a little higher up from the base of the trunk.

    Alan in MI

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