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Air Guns Crosman Precision Diopter Sight System: Part 3

Crosman Precision Diopter Sight System: Part 3

Crosman sight system
The Crosman Precision Diopter Sight System.

Part 1
Part 2

This report covers:

  • The test
  • Here we go
  • Elevate the sight
  • Cant the rear sight
  • Cant right
  • What happened?
  • What to do?
  • What have we learned?
  • Summary

Today I do it. I intentionally cant the rear Crosman Precision Diopter sight to see whether that has any affect on the point of impact downrange. Some readers have said if we sight through two holes cant shouldn’t be an issue. We shall see.

The test

To get the greatest separation between groups , if there is any, I shot today’s test from 25 yards. I shot from a bench with the rifle resting directly on a sandbag. I shot 5-shot groups because that’s all it takes to see this.

There won’t be any group measurements today. That’s not what this is about. It’s about whether canting affects the placement of the group when the rear peep sight and a diopter in the front are used. How can two holes be tilted? Some say there will be effects you can see and others say no.

All the shots will be with the Qiang Yuan Training pellet. The Crosman Challenger 2009 likes that pellet a lot.

As I cant the rear sight I will do nothing to the front sight. Remember there are another set of inserts that permit canting the front sight insert just like the rear sight. I am not using them for this test. I’m using the inserts that remain fixed, so as I cant the rifle I’ll see the crossbars that hold the front aperture become tilted against the target.

Here we go

I decided to shoot the first 5 shots with the sights set where they were for the last test in Part 2. They landed in a vertical group at the bottom of the bull. I have no explanation for the verticality of the group, other than the shot at the bottom is what makes it vertical. Take that one away and the group looks more roundish.

Elevate the sight

After the first group I dialed in 40 clicks of up adjustment. That took the next five shots straight up to the top of the bull. That group went up just less that 2 inches.

Crosman Precision sight centered
The first two groups were shot with the rear sight centered in its holder. In other words, not canted.

Cant the rear sight

Then I canted the rear sight to the left. All it took was loosening the one Allen screw that clamped the rear sight “barrel” and then rotating the sight. The sight only rotates as far as the lines on the sight barrel.

This time the five shots went to the left of the last group, the one that is 40 clicks up from the first group. But they didn’t land lower on the target (than the last group fired) as I expected. I also found myself intentionally trying to cant the rifle back to the right to level the bar that holds the front aperture. You will notice that this third group is especially large. That’s from me not canting the rifle that same amount each time. Phooey!

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Cant right

Next I canted the rear sight to the right, which works the same as the left, only in the opposite direction. This time I took pictures for you. 

Crosman Precision sight canted right
The rear sight is canted to the right.

Crosman Precision sight canted straight on
This is what it looks like straight on when the sight is canted to the right.

What happened?

Well, this time I decided to level the front aperture one every shot. I did so because I now knew I couldn’t get it canted correctly (the same) for every shot. And this time all the shots went to more-or-less the same place as when the sight was elevated by 40 clicks. In other words, they DID NOT move to the right as some of us expected them to — at least not very much.

Enough talk. Let’s look at the target.

Crosman Precision sight first target
First target. Here’s whatcha got. First five shots are at the bottom of the bull. Then 40 clicks up and the next 5 are straight up from that. They’re the holes to the left of the big group at the top of the target. Then I canted the rear sight to the left and five shots hit to the left of the bull in a very large and open group. Finally I canted all the way to the right and five more shots are at the very top of the bull. Yes, there is a little separation between those shots and the second five shots, but not that much! In fact one of the holes from the second five shots is inside this final group to the right.

What to do?

BB was puzzled on just how to proceed. But the one thing he knew he could do well is level the front sight insert bar every time he shot. That is what he did on the second target. He started by shooting five shots with the rear sight canted to the right (while leveling the insert bar), as it was at the end of the last target. Then he rotated it to the left and fired five more shots, being careful to level the front sight insert bar for every one of them. Then he centered the rear sight as it had been at the start of today’s test and fired five move shots. And finally he lowered the elevation by 40 clicks straight down. Let’s look at that target.

Crosman Precision sight second target
The second target is telling because I leveled the front sight insert bar on every shot. There are 15 shots in that group at the top. Why the group at the bottom is over to the left instead of at the center on the bull, left and right, I have no idea. 

What have we learned?

I believe that we have learned that the people who said two holes cannot be canted with each other were right. However, I’m not certain of that. 

I also know that when I see the front sight bar tilted against the target there is a natural tendency to level it. The bottom line is, I think this feature of being able to cant the Crosman Precision Diopter Sight System isn’t one I care for. I won’t go so far as to call it a failure, but it isn’t a feature I would ever use.

I didn’t try this with the front sight inserts that also cant with the rear sight. From what I see here as long as the front sight appears level, the pellets go to the same place. Yes, canting the rifle (front sight) does move the shots, but it’s not as clear and precise as when shooting with a scope that’s canted.

Maybe I’m missing something and need to be instructed. That is a distinct possibility. But for now, at least, I will shoot with the rear sight leveled, side-to-side.


Wow! This is a result I would not have predicted. I sided with the ones who thought that canting left and right would move the groups from side-to-side. And I admit that they did move, but the way I did the test it’s too difficult to maintain the same degree of cant every time.

Do I need to repeat the cant test that I did years ago with a scope? I think I know why that test turned out as it did, but first I’d like to hear from you.

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

24 thoughts on “Crosman Precision Diopter Sight System: Part 3”

  1. “The bottom line is, I think this feature of being able to cant the Crosman Precision Diopter Sight System isn’t one I care for. I won’t go so far as to call it a failure, but it isn’t a feature I would ever use.”
    I concur with your assessment. I have a couple of guns where my rear peep sight is canted, the lateral plane of adjustment is not perpendicular to the front post. It’s no big deal; I always hold the front post vertical; but on the rare occasions when I have to adjust these sights, I have to make lateral, and small vertical, adjustments to get the pellets to go where I want them to go. Fortunately, these are not target rifles, so they rarely require adjustment. One of them is my old Sheridan; I’ve only had to adjust the sights 5 times or so in 35 years (basically, when I switch to a different pellet)…I can live with that. 🙂
    Blessings to you,

  2. What I see is with the canting of the rear sight to match the front is sighting in the scope.

    If I need to move left a 1/4″ and down a 1/8″ and the rear sight matches the front sight cant will move more correctly for the clicks that are used.

    Bottom line that is what having the rear sight canted the same as the front sight does.

  3. BB,

    Now that I have seen how it is supposed to work I cannot imagine it being used unless the shooter has a severe canting problem that they have to work around it instead of working on it (not sure so sure if I got the intention right). In most cases correcting for cant would concentrate on the front sight anyway. Maybe it’s a solution looking for a problem?


  4. The purpose of the canting of the front and rear peep is to compensate for a person’s hold. Very few people will hold a rifle perfectly level. The idea of canting is to put all adjustments in the horizontal and vertical plane. This is why bubble levels are not allowed in 10-meter competition. These days many competitors use the clear front iris. It totally eliminates the eye/brain issue of trying to level the sights. You have the rifle adjusted to where it is comfortable for you at your natural aimpoint, and the sights are adjusted accordingly.

    • This is exactly correct. The quality 10m air rifles are designed to be adjusted to maximize the stability and consistency of the hold, In the standing position the body is somewhat contorted to to that end, and may require canting of the rifle to get the eye where it belongs all the while allowing the shooter to keep the head vertical (for balance) and held up to prevent undesirable muscle tension. Without the ability to adjust the sights for the cant angle, horizontal and vertical clicks will interact in a very predictable way depending on the angle – dig out your high school trigonometry text book for the numbers. Someone posting about the angle of the front sight being irrelevant is right, hence the clear inserts; however, without the bars or some other means, any significant cant is difficult to replicate precisely on each shot, and that precision is what is it all about. Anyone who cants the rifle either standing without support, or on bench position, would benefit by knowledgeable use of adjustable for cant rear sights and and probably front sights with a bar, or a bar and cross. The longer the range, the greater the effect, and the more valuable the knowledgeable application of the sight correction for the rifle cant.

      I always shoot standing unsupported. I cant a lot, I have short arms, a large chest, and a long neck, so I maximize the use of rifle adjustments to deal with these facts – high sight risers, maximum palm rest drop, high cheekpiece position and offset, and offset sights with cant angle addressed. See attached photos of my FWB 800W with these adjustments available and used.

      To get the rear sight synch’ed with the horizon once a good position is achieved, 1) align front bars with a horizontal line (target border); 2) loosen the rear sight fixers and put a straight edge on top; 3) rotate the rear sight until the straight edge is parallel with the front bar and tighten the fixers. Do this one time.

      • I just went through a bunch my aperture sights. Anschutz, Diana, Walther, Weihrauch and Gamo all have the same M9.5 x 1 thread and freely interchange. somethings definitely wonky with your Gehmann.

        If I recall correctly, your Gehmann aperture didn’t fit the Air Force adaptive sight either, is that correct? Something’s not making sense. I’m wondering if that Gehmann you have is a PH510 model with a 7/32″ thread made to fit the Redfield International, Olympic and the Lyman 90MJT?

  5. From what I see, this sight allows the optic to rotate about the centerline of the unit, but it does not shift laterally at all when adjusted. This observation is the basis for what I say below – if not the case, then my comments below on this sight are not correct:

    I would not describe this sight as a true canted sight, but rather as one that allows the shooter to visually eliminate the distraction of any natural cant that they may have in their stance and hold. Since the intended shooting distance for this gun is always 10 meters, the key is consistency of hold, not actually eliminating cant. So this sight would enable one to feel more confident in their shooting, but it would not actually “eliminate cant” – in fact, it would work to “standardize cant”.

    Technically, cant is not having the optic rotated off of vertical, but one of not having the centerline of the optic not directly above the bore line. If the optic is off to the side of the bore, but the rifle is held tilted such that the centerlines of the bore and optic are vertically aligned (whether or not any crosshairs are horizontal, but ideally they would be so the shooter knows they are holding correctly), the rifle is not actually canted when it is shot – this would be a true “canted optic” sight.

    If one “cants” these sights differently and then holds the rifle so the sights are level at the target, they will be inducing cant into the rifle and it will show up on target as different POI – because they have to cant the rifle to get the sight picture level. But if they set it up once to work best for them in a canted position, and hold it consistently every time (and always shoot at the same distance, which is the game here) then they won’t have any variation in POI from the physically canted set up.

    A true canted optic would need a mechanism that would shift the optic off the bore axis and allow for rotation to get the appearance of a properly leveled rifle. But that would be excessively complex for a rifle that is always shot at the same distance.

  6. There is a guy at the range that shoots only 10M. For his rifle hold, he hold the gun at about a 20 degree angle. he does this so his head and cheek weld are consistant. At his 10 M he is spot on. At any other distances he is not…


  7. B.B. and Readership,

    Time to stop this charade! This sighting system is for those that actually hold the rifle with their bodies position. It is used to fit the rifle to the body with the least possible chance to require muscles to make the shooting position that results in the Natural Point of Aim to match the X on the Bullseye; nothing more nothing less.
    As an example read the following:
    “The plump shooters and female shooters with big breasts
    The challenges that shooters with these body shapes face are:
    • The balance of the rifle is moved further away from the body,
    • In the shooting position, when the rifle is parallel to the shooter’s chest, there can
    be contact between the rifle and the left part of the shooter’s chest, which is
    against the rules.”

    The rifle has to be as close to the body center line as possible.

    The UIT Rules do come in to all this heavily. If you want to know more you need a qualified coach!


    • Shootski,,, and anyone else,

      I think that everyone agrees about what can’t actually is,, that is that the rifle is held in a way that the sight line is not directly above the midline of the barrel.

      That being the case,, one can attempt to correct this by shifting the hold on the rifle until both lines are “plumb”. OR,,, they can simply adjust the sights to a place where the two lines coincide at a particular distance.

      From what I can tell,, the purpose of this sights “canting” adjustments are to make adjustments to the point of aim easier for those who choose to keep their “cant”. In other words,, normally when one adjusts the vertical POA by a certain number of clicks, the POI rises vertically. If the rifle is canted and one does this the POI would move both up AND in the direction of the cant.

      Using this sight,,, and I am guessing a bit, here,,, one would need to use the front sight that adjusts as well as the rear sight in order to maintain the same cant while testing this theory. I think that a clear front sight would make it very difficult to maintain the same cant for several shots,, as shown by BB’s test.

      As with most of the rest of the commenters, here, I quite agree that I won’t be purchasing this accessory.


      • edlee,

        This may keep you and everyone else from needing to guess:
        ISSF National Coach Course
        Shooting Positions
        © By Goran Maksimovic

        Cut and paste the above into your Browser of choice and you should get a PDF of about 2.5MB and 90 plus pages of the kind of shooting this sight system is meant for. Most of the Zero Point is obtained without even a thought to the front and rear sight. Once all the early hard work is done the sights are adjusted to the shooter rifle system for each of the three positions.
        This is not the shooting that most of the readers of this blog do!
        These sights can be used to good effect by all of us but not like a trained 10M shooter.


        • Shootski

          Yep,, I have it in pamphlet form. Mine is from 10 years ago,, but I think the important parts are in both.

          I participated in three position 10 meter competitions for a few years. As a paraplegic, there were slight modifications for us. Either way, tho,, the separation from the chest could be paper thin and still fulfill the ISSF rules, so canting of the rifle was possible,, and quite obvious for some of us.

          The important part was to have the same orientation of the rifle in all positions so that sight adjustments wouldn’t be needed ( tho , personally, I used the sighter bulls to make sure even when moving from target to target when we had double holders).

  8. B.B.,
    Off-topic of today’s report, but airgun-related, I finally got my Dragonfly Mark2…
    (the rifle on which you reported here):
    …proved out to the point that I can declare victory, and say it is exactly that for which I was looking.
    The rifle has more power than my old Sheridan, and with much less pumping effort.
    The gun can be scoped, and held by the rear mount to pump it with no stress to scope or gun.
    (but I did have to shim the rear mount with a 1/16″ soft steel shim…and another .020″ of shims!)
    To prove things out, I used a simple Leapers UTG 4X32 AO Mil-Dot scope I had lying about
    (and some mounts, courtesy of RidgeRunner…thanks, man! =>).
    Once I got things trued up, and put some Blue Loc-Tite on the threaded boss (thanks, Gunfun1! =>), I was able to shoot a somewhat decent group at 25 yards (using 10 pumps); the group could have been better if: A) it had been shot by you, or B) I wasn’t so worried not to wound the doe that decided to feed right behind the 25 yard backstop (to be fair, that’s my fault; she feeds there all the time; hence, the “trespasser” was ME! =>).
    Anyway, I have a nice. lightweight, well-balanced, relatively-powerful, and accurate pesting rifle…that also happens to be just plain fun to shoot. It’s everything you said it would be; the trigger is nice and predictable, and no matter where or how I hold it, it shoots the same…very cool!
    I guess I should also post this in the comments under part 4 of your excellent report on this fine rifle. 🙂
    Take care & God bless,
    P.S. I’d like to give a shout out to Leapers! As you can see in the pic, this second-hand scope has no turret covers; I called Leapers today, and spoke to Miss Rachel (a wonderful and helpful Saleswoman). She is sending me new covers for the windage and elevation turrets, as well as a set of scope covers…for free! I told her I had 3 of their scopes and planned to buy more. She told me that they have a discount for Police, Military, and ALL First Responders: Fire Fighters, Paramedics, the whole lot…how cool is that?…pretty cool! I wish more airgun companies would follow that lead. 🙂

    • thedavemyster,

      Nice shooting even with that freeloading Bumbie making you all concerned about shot misplacement. Lol!
      It looks like pellet experimentation will be a Cakewalk given your early results.
      Hope she shoots long and well with no trouble.


      • shootski,
        Thank you! The one thing that concerned me, not being able to store the gun with a pump or two in it, was addressed by Mike in Atl (thanks, Mike! =>): “You can just put a pump or 2 in then hold the bolt back and pull the trigger and ease the bolt forward, Done.” After he said that, I went back to part 1 of B.B.’s 4-part report, and lo and behold, B.B. had already addressed that…but that was WAY back in February…the old dave brain has trouble retaining info for that long! B.B. did such a great job in his reports on this rifle, that I just HAD to get one!
        And I’m happy that I did; as you said, there is more experimentation to be done to find the best pellet, yet things are looking good already; I am well-pleased with this addition to my small stable. 🙂
        Happy shooting to you,

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