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Competition Scope dope — I hope! Part 1

Scope dope — I hope! Part 1

by Tom Gaylord, a.k.a. B.B. Pelletier

I recently said that, with all the new readers of this blog coming from the firearms world, I need to concentrate on the fundamentals. Today will be such a report.

I was at the range on Tuesday and watched a familiar problem play out. Only this time it happened to a firearm owner rather than an airgunner, and I believe that is why it was such a problem. Airgunners are conditioned early that their scopes don’t look where the barrel of the gun points. Not so for firearms shooters. They seem to take it for granted that the barrel is in alignment with the axis of the scope — which is almost never is.

This shooter was experiencing problems getting her .243 Thompson Center Encore sighted in. I was three benches away and here is what I saw. She kept adjusting the scope up and up, and it didn’t want to go as high as she needed it to. She finally got on target, but she was getting 5-shot groups with three close together and two about 4 inches away at 100 yards. This was a rifle that was known to be accurate, and she had already shot a Ruger .204 Encore several times this same day, getting inch-sized groups. So, I knew she could shoot.

I could diagnose this problem in my sleep because I’ve seen it hundreds of times. But do you know what was happening?

The problem
The scope was adjusted too high, and the erector tube spring was relaxed, so the erector tube that holds the crosshairs was bouncing around with every shot. Sometimes, it would stay put, and other times it moved. The result was a shifting point of impact.

I saw that her scope was a cheap one. It had two things going against it. First, it had the kind of adjustment knobs that provide no feedback about where you are in the adjustment range. When you adjust the reticle all the way up, you can’t see that you have. Second, because the scope was a cheap one, its erector tube spring was also cheap. That means the useful range of adjustment before the spring relaxes and allows the erector tube to move is quite limited. In short, these scopes get into trouble a lot sooner than scopes that are better made.

cheap scope adjustments
A scope adjustment like this gives you no feedback on where the elevation is set. It’s easy to adjust up out of the range where the erector spring holds.

AirForce 4-16X50 scope better scope adjustment
This adjustment knob tells you at a glance (by the vertical index marks) how much elevation is applied. This is a so-called target knob, but there are many scopes whose adjustment knobs have covers and work the same way.

How to check for this problem
My shooting buddy, Otho, was mentoring this lady, and he called me that evening to ask what was happening with her gun. I told him about rifle bores never aligning with receivers or scope bases, and he understood right away because he’s drilled and tapped dozens of vintage rifles to mount scope bases. He knows very well that a rifle bore will seldom line up with the top of the receiver or with the scope mounts.

I walked him through the problem with the scope that I mentioned above. It turned out that the lady’s husband had switched scopes on that rifle and, of course, nobody knew where the current scope was in its range of adjustment. If it had been on a drooper firearm before, it might already have been adjusted high in the elevation range; and what she had to do to get the Encore on target on this day might have pushed the vertical adjustment into oblivion.

I have to stop for a moment and answer a question that is bubbling up in someone’s mind. If the scope can’t be adjusted beyond a certain point without causing problems, why don’t the manufactures limit the adjustment range? Why, indeed?

Why do you suppose automobile speedometers go up to 120 MPH when the cars they are in will only hit 98 on a perfect day going downhill? Because it’s easier that way. They sell more cars that way. Because the companies who manufacture speedometers only make them certain ways, and the car companies have to buy what’s available. Etc.

Oh, don’t you dare tell me speedometers are all digital these days! I know that. I’m making a point, and you know very well what I’m saying.

There is an easy way to check this — to see if I’m right, or if something else has happened. All you have to do is dial the scope’s elevation back down 40-60 clicks and shoot again. Put the aim point on a large piece of target paper with lots of room below it and see where the shots land.

While you’re at it, run the windage adjustment to the left 40-60 clicks, too, because adjusting too far to the right is the same as adjusting too high; and on many scopes, there’s only a single erector tube spring set on a 45-degree angle to both adjustment knobs. If you get a tight group with these shots (regardless of the fact that it’s low and to the left), you know that the erector tube was floating before. The solution is easy.

Unertl scope adjustment knobs return spring
This shows how an internal erector tube is adjusted. Even though this is an externally adjusted scope, it works the same. The spring is at the 5 o’clock position inside a blued steel button. As either adjustment knob is turned, the spring inside the button compensates, keeping tension on the scope tube at all times.

Fixing the problem
It’s perfectly okay to own and use cheap scopes. I have several of them that work fine. As long as you keep the adjustments in the range where the erector tube spring can do its job, these scopes work fine. When there’s a sight-in problem, raise the rear of the scope enough that the vertical adjustments are closer to their center (from stop-to-stop according to their clicks — not optically centered), so there’s tension on the internal spring.

If you have a gun that shoots to the left, you may also need to adjust the rear of the scope to the right for the same reason. Adjustable scope mounts are the easiest way to do this; though, for small corrections on elevation, shimming under the rear scope ring will also work.

Why do guns always shoot low and to the left?
I don’t know. Why does the doorbell always ring when you’re about to get in the shower? But before some mathematician starts wondering why barrels don’t shoot high and low equally often, let me just say that they don’t. They tend to shoot low far more than random chance would allow. And they also tend to shoot to the left more than they do to the right, although left (and right) is far more unusual than down (or up).

The point
The point of this report is not to convince you to buy expensive scopes. I can’t afford to do that, and you don’t need to, either. What you need to do is understand this problem, which is by far the most common scope problem for both airguns and firearms, alike.

Once you understand it, you won’t condemn every scope, crying, “Scope shift!” when the problem is really one that can be easily solved. And maybe you’ll pay more attention to the adjustment knobs on those bargain scopes in the future and look for ones that give you feedback on where the adjustments are.

One last thought. Scopes that are less expensive will generally have less useful adjustment range in either direction. So keep a close eye on them. As long as the return spring is kept under tension, there’s no reason these scopes shouldn’t work very well.

76 thoughts on “Scope dope — I hope! Part 1”

  1. Doesn’t matter if you’re a baseball player, hockey player, golfer, bowler, trap shooter, rifle shooter, etc. if you do it long enough you need to be reminded of fundamentals.

    Don’t know if it’s because I overlook the obvious because I assume that intuitively (subconciously? LOL!) I’ve already checked those obvious, fundamental issues or if it’s because I get too arrogant but it’s amazing how many times I’m looking for an advanced problem with it’s just a silly fundamental issue.

    Since we’re talking about scopes running out of adjustment and floating erector tubes along with potential solutions rather than my basic stupidity I’ll throw barrel bending into the mix as a potential solution if minor shims can’t fix the problem and adjustable mounts or a scope with a greater range of adjustment aren’t an option.

    These “fundamental” articles are priceless. The potential additional readership to this blog these fundamental articles could generate from all shooters is tremendous IF those shooters can find them in the future while doing an internet search.

    The title won’t help in a search for the problem that being talked about. I think more shooters from all walks will find this information in the future if the title was something like, “My Rifle Scope Ran Out Of Adjustment”. I’m thinking of an ideal title for internet search that fits this topic but I’m sure others could chime in with a more elegant and more spot on title that could result in greater hits in the future.


    • Kevin,

      You are absolutely right about the fundamentals being the reason why people slip. Even the most advanced shooters fall because they’ve somehow lost some fundamental. A common one is lack of follow-through. Over time your follow-through may get shorter and shorter by tiny but incrementally additive amounts. Suddenly, you’re dropping points where you haven’t in years.


    • Kevin,

      Thanks for the insight. Instead of changing the title, I’ve added the appropriate terms to the keyword search. That will help just as much as changing the blog name when it comes to searching in Google.


  2. I had this happen (or should say we had this happen) with a break barrel springer. I had taught my Daughters to shoot with my old Crosman 760 with open sights. They were pretty use to the 760 after a fair amount of time shooting it.
    So I figured it was time for a change. We got a break barrel springer and I put a scope from a .22 rimfire gun with a one piece scope mount on the gun.

    So here is where I went wrong.

    Didn’t test any pellets first. Was using 10.3 grn. .177 cal. pellets. (Too heavy for that particular gun )

    Target was placed to far out. About 35 yrds. (again too far for the guns fps it was shooting with the heavy pellet)

    And the scope looked like it was set on 4 power when it was set at 9 power on the magnification
    (the scope was just made plain straight up cheap).
    I guess the only reason it worked on the .22 rimfire is that it had about 500 fps more velocity going for it verses the springer.
    And we were shooting at a plastic gallon milk jug at about 30 yrds. Not a fixed secured paper target. So precise placement wasn’t a issue.
    We were just having fun hitting the target (milk jug).

    Just like BB was saying we were max-ing out the up adjustment on the scope to try to bring the point of impact up to the aim point of the cross hair on the target bulls eye.
    The farther we adjusted the scope up the worse the group of the pellets became.

    Then the next few changes was like a wave of the magic wand.
    Lighter 8.3 grn. pellet.
    Moved the target into 20yrds. away.
    Adjusted the scope back to the middle.( I don’t know if this is the right way to accomplish this; but I adj.the scope all the way up with out forcing it then count how many turns back down till it stops. Again with out forcing it.
    Then adj. back up half the amount of turns and that should be the middle of the adjustment for the up and down.
    Then do the same to the side to side. The scope should then be set pretty close to the middle of the travel ).

    Then just start shooting and zero the scope back to the bulls eye.
    The springer went from a erratic 3 1/2 inch groups at first down to 1 1/4 groups.
    And recently I put a better scope on the gun ( and I don’t mean a more expensive scope.Just one with better features ). The gun now shoots at 35 yrds with 1 inch groups. That’s a big difference. 3 1/2 inch’s down to 1 inch at 35 yrds.

    So if I would of left the scope alone and told them to just go ahead and shoot the gun at the 3 1/2 inch groups they may of got discouraged shooting. And maybe wouldn’t be as anxious the next time to shoot. And on my part that would of been a big fail.

    Its just amazing how easy it is to overlook something in any type of activity that you get involved in. And whats worse is when you just don’t have any idea what is happening. That’s the kind of stuff I get to have fun with at work. But I do like when you get it figured out. Usually good results will make happy faces. And that’s whats in my mind when I’m trying to get something accomplished.

    It is just always amazing to me how something looks so simple when you first see it. And the more you are around it the more complicated it really turns out to be.

      • B.B.

        I won’t count clicks to center adjustment range or do an optical center either one. I have some scopes that have taught me that these ideas can fool you badly and cause you a lot of grief. You have to know the scope before you should think about doing these things. Even then, the scope can have started going bad and is no longer like you thought it was.


    • Michael,
      Most right handed shooters have to fight the tendency to allow the gun to drop down and to the right as soon as the trigger is pulled. As a left handed shooter, I have to fight down and to the right. The solution is to hold your body still after the trigger is pulled to allow the pellet to exist the barrel before you release your sight picture.

      David Enoch

    • Michael,

      Where twist direction does affect direction of a bullet is with wind. For instance, for right-twist rifling, wind from the left will cause the bullet to go down and to the right, while wind from the right will cause it to go left and up. So twist direction will cause an approximate diagonal pattern depending on wind direction and strength.


  3. BB,
    Early on in my airgun education, I had the exact problem you mentioned. I chased pellets all over the target because I didn’t understand that my erector tube was floating. The scope was an old Beeman Blue Ribbon 66R which has very good optics but limited scope travel.

    Please do a follow up article showing how the shim a scope, show the option of an adjustable mount, and has Kevin suggest, barrel bending if all else fails.

    David Enoch

    • David,

      I thought about a follow-up report with scope angle corrections — just as you have suggested. I wanted to see what the reaction to this report was before doing it.

      It isn’t you veterans that I’m concerned with. It’s the newer airgunners who are coming in from firearms. They aren’t as used to the barrel angle problem.

      So, we’ll see about a follow-up.


        • Thanks for giving me that idea. I’m trying to mount a Tasco Propoint dot sight on my new Crosman MK-177 and just couldn’t get the elevation to go low enough to get it on target. I shimed the back of it with a bunch of folded up paper to get it to put the dot on my aim point (using a laser boresighter). I was thinking about doing that but this comment got me motivated enough to pull the thing out of the rings and try it. I hope that helps the thing be a bit more user friendly. I’ve been busy making it so I don’t have to fight with it in order to fire it for a few hours. I think I finally got it right.

      • BB, and all,
        ” I wanted to see what the reaction to this report was before doing it.” Although I have only posted maybe 6 or 7 times ( learned to read– never to type ), which is why no-one will recognize my name, I have been reading your blog EVERY day since I found it in Feb. 2007. So I consider myself a veteran reader. I decided to spend the HOUR it is taking me to type this (no exaggeration) to assure you that these types of blogs are without a doubt my favorites. Thank you for teaching me everything I know about airguns, and please don’t stop writing. JR.

        • JR,

          Than you for taking the time to respond today. I need to know that there are people like you who appreciate these kinds of reports. I will definitely follow up on this one and give you the whole picture on scope alignment.

          Thanks, again,


  4. MORE Scope Dope, I Hope! New to air gunning, yes. Limited rifle/scope experience since I’ve been a shotgunner for many years. Sooooo, any more scope info you can impart would be a plus for me. Thanks B.B.

  5. I have one gun that has always been a problem child with a scope. My Gamo Whisper. It’s one of the old ones with the steel triggers. I think it’s one of the first ones that Gamo made. Not quite sure. It seems to do fine with the fiber optic sights and I have taken a few pest birds and a few muskrats with it. But when I put a scope on it. Doesn’t matter if it’s an expensive scope or a cheap one, It can’t seem to hit the wall of a barn while standing in the barn. I have scopes on quite a few other guns and have no problem at all with any of them when using a scope. But for some reason I can’t seem to figure out I don’t seem to be able to work with a scope on that whisper. It’s like trying to ride a horse that isn’t saddle broke and make it to town on it. Just isn’t going to happen.

    • John,

      The problem you described is sometimes caused by the breech block hinge bolt not being tight enough. It allows side-to-side play at the muzzle. And because both of your open sights are located on the barrel the problem only surfaces when using optics (mounted on the sping tube). Also check your chisel lockup tightness for up-and-down play at the muzzle; and of course the stock screws.

      David H

      • One day I’ll pull it out of “the rack of forgotten guns” and work on it. I’ll look at these things and see if it has loose parts. At the moment I’m trying to make the crosman MK-177 a bit more user friendly. I’m finding it very hard to use as I have to fight with it to pump it and cock it.

  6. A delivery company is only as good as its weakest employee. If the driver is terrible, then you will have unhappy customers on that route.

    Pyramyd AIR has used FedEx for some time. They switched over to UPS a few years ago…and then switched back about 3-4 months later.

    I have my own horror stories regarding UPS, USPS and FedEx…but FedEx has been the best so far in 99% of the delivery situations.

    Remember, FedEx didn’t have a delivery service that competed with UPS. It was only when UPS employees went on strike that FedEx stepped in and said they’d offer temporary delivery service to make up for the shortfall. That’s when FedEx decided that this was a good deal and their temporary delivery service became a permanent one.

    If you have terrible service from FedEx, UPS or USPS, then it’s the person in the truck and/or the local distribution center that has to fix the issue.

    We once had an unfortunate delivery issue with FedEx that involved a laptop computer sent to us instead of a home on the next street that had the same house number. The lady who owned the computer apparently did an excellent job of blasting them out of the water…from the driver to the local distribution center and right up to customer service at HQ. We’ve had really good service ever since then.

    If you’re miffed, don’t just yell at people…do an online search to find out the names of the top execs for a division and write a really good letter that lays out the problems, using specific times & dates. I have used this approach in several situations and have gotten apologies and have seen positive changes in service. When you are meticulous and can show times, dates, conversations, who did what, who said what, etc., people see the documentation and usually believe your side of the story.

    • Edth,

      I was a mover of household goods for many years. And I always tell people shopping for a moving company. It’s not going to matter which company you hire unless the guys who actually show up enjoy doing a professional job and take pride in treating your stuff like it was their own. So ask the company to send their best movers. And good luck.


    • Turns out my messed up fedex shipment was due to fedex putting a new driver on this route that wasn’t familiar with the area. The guy has only been driving for fedex for a week So he went to the wrong apartment in another part of town. I guess I’m lucky nobody was home to take the delivery there yesterday or my Crosman MK-177 would have vanished into thin air and I would have been really mad. As it is I couldn’t bring myself to climb all on the driver as he was new at the job. I finally made the MK-177 more user friendly. But I’m really wishing the cocking knob was on the right side. Body memory keeps making me go for the nob on that side. When it’s not there it throws me all off.

  7. Off topic….

    Anyone watch American Airgunner last night ?

    The only thing that caught my attention was Paul cleaning a cheap break barrel .
    Cleaning from the muzzle end with a brush dipped in some kind of solvent. And also mentioning that a patch could be pulled through the barrel with wire too !

    I think that this is worse than the episode in which the head Umarex guy checked screw tightness with the rifle placed upside down on the workbench…..on the sights !


    • I know how you feel (esp. on a b-barrel), but unless he is using a file as a cleaning rod after each shot, it is unlikely to hurt — I know a few rifles that have never been cleaned from the breech end :)!

      Also, I remember reading about the fishing line cleaning (not wire though): Apparently people used the muzzle like a “pulley” and abraded grooves in it. Even at that, I wonder just how often they were cleaning…

      • BG_F

        Over time I have seen how little damage to the crown that it takes to waste the accuracy. I have become extremely protective of good shooting barrels. My methods have changed over the years to that end.


        • The lovely Crystal Ackley did a bit on barrel cleaning for American Airgunner using the plastic line for a lawn trimmer. As I remember she routed the line through the breech. Is it strange that the supposed eye candy of the show had a better segment on barrel cleaning than the show’s main host? I don’t think so. She was a hell of a shot too.

  8. We’re never to experienced to make stupid mistakes!
    A couple of weeks ago I was at the range with my Savage .22WMR.
    My first 5 shot group (100m) was nice and tight, about an inch…but about 1.25″ left of my POA because there was a steady 10-15mph breeze.
    So I dialed in 5 clicks.
    And it was worse.
    I dial in some more and it was no better.
    At this point I became frustrated…the groups were tight, they just WERE NOT going where I wanted them to.
    Then it dawned on my (I’ll try to explain this but a visual would help)
    The scope windage dial has the ‘R’ arrow pointing to the right (of course).
    So I was looking at the dial…looking left of the ‘R’ and determining how many clicks to move. I then moved the dial to put the ‘0’ at that postion (I can reset my zero).
    I was looking to the left of ‘R’…not even thinking that to do this I was actually moving my POI further left each and every time.
    Finally, after I was actually off the paper this hit like a lightening bolt…I put the ‘0″ back to centre and there were my shots…all about 1.25″ left of the 10x (the wind hadn’t died).
    Moved 5 clicks in the proper direction and BINGO…the next 5 shots formed a nice tight cluster on the 10x ring.

    • Been there, done that, and likely will again! Not just scopes either — on my BP rifles, there is the option to drift either/both the rear and front sights for windage (on initial sight-in). The rear is pretty easy, but it is usually best to divide the full correction between front and rear sights, so I usually end up talking to myself about how counter-intuitive adjusting windage with the front sight is, getting close, then going the wrong way on the “final” adjustment after my confidence gets too high :)!

  9. Ain’t much of a shooter, know a little about ridin’. When it won’t fire on the first kick or these days a click, first system check is the tank. Those nasty little gas gremlins will steal your push water. Have a name for those that trust their gas gauge, they’re called, “Doh!” pushers. The more ya know, the more complex ya make the fix, when the majority of the time, it’s just a k.i.s.s.

    Mr. B.B., fought a shim challenge just 2 days ago. Yes, please, more dope.
    Thanx ya’ll. Shoot/ride safe.

  10. Just got the new crosman MK-177 today. I knew it would be an all plastic gun. so that isn’t a let down. What is a huge let down is just how hard the gun is to actually use. The pump lever needs to be pried open foe each pump and for a right handed shooter the cocking lever is very awkward to try to use. On top of that all the innovative things like that selector that switches from bb to pellet are molded in and don’t actually do anything. The magazine storage is also molded in. In order to get into the clip storage and the place where the sight tool goes you need a small screwdriver to pry with. So you need to carry tools in order to get to the tools. In all Crosman seems to be going down hill on building airguns. This MK-177 is going in the closet of forgotten objects today. It’s a shame really for all the grief it took to get the thing.

    • I’ve been fixing deficiencies with the new MK-177 today. So far I cut a notch in the bottom of the butt pad so I could get it open without using extra tools. Then I took a dremel to the inside of the pump so I didn’t have to struggle to pump it. Then filed down the front sight so I could get a proper sight picture. Sadly there is no cure for the awkward left side cocking lever. If that was on the right side with all the work I had to put into it to make it useable out of the box it would be a decent gun.

  11. BB,

    This is the perfect time to ask about something that I have wondered about on this issue, and it was prompted by the comment about the shooter’s scope possibly having been on a dropper gun before (as well as people often recommending centering scopes before mounting them).

    What difference can optically centering (or centering by counting clicks) make to the final scope adjustment when it is installed on the gun? Similarly, how can it matter how it was adjusted or what gun it was on before?

    As I understand the optics, for a given mounting set up at a given range, there will be only one setting of the scope that will align POA and POI . It should not matter where one adjusts “from” given that the person has only one place to “go” to. If the scope ends up out of adjustment when mounted on that gun (with those rings set that way, at that distance to target, with that ammo) it will always be out of range in that configuration. Of course this is different than what Gunfun1 described, because in that case he changed to a lighter pellet with a different trajectory and used a different distance to target.

    That said, I do see value in centering the scope and then switching rings around (or trying multiple sets) to find the best starting point before adjustment, but that is not what was implied in the blog.

    Any thoughts?

    Alan in MI

    • Alan,

      If the scope in question was mounted on a drooper before, the vertical adjustment will already be set high. And if the adjustment screw is like the one in the first picture, you won’t know that it is set high.

      So, if the rifle you are now trying to sight-in with this scope droops even more than the last rifle did, you will adjust the scope even higher — without realizing how high it was already set. After only a few clicks of elevation (on top of many previous clicks of elevation that you don’t know about) you may reach the place where the erector tube starts bouncing around.


      • BB the scope I was talking about that we had the problem with was like the scope in the very top picture of this report.

        I think maybe I didn’t word my explanation correctly. We are both achieving the same result. We just counted the rotation of the adjustment screw differently. If you open lets say the up adj. screw all the way out then all the way back in. Then go back up half the distance you will be at the center of adj. Scope zero. The adjustment knob is kind of like a plus/minus gage from the center of adjustment travel. That’s the way I look at it.

        Both scopes in the top 2 pictures above will eventually stop when you reach the full up movement.
        But the scope in the second picture will give you a visual of how far the adjustment knob traveled up wards before it stops. Then if you screw it all the way down till it stops and you see what line it ends on. If you come back up half the amount of lines you have on the scope you should be pretty close to in the middle of the adjustment. Scope zero.

        Same way if you adj all the way up till it stops then counted clicks all the way back down till it stopped.Then go back up half the total amount of clicks. Again you should be in the middle of the travel. Again scope zero.

        Did I word it maybe better this time? Not trying to be sarcastic or anything but the fingers don’t want to type what the brain is thinking sometimes.

  12. Hi B.B.,

    I recently sent my .177 Benjamin Marauder to Crosman to replace the fill adapter assembly which had been leaking since I purchased it a couple of months ago. After I got the airgun back I noticed that it was now losing 350 psi per 10 shots vs losing only 200 psi per 10 shots when I first bought it. I was able to talk to the tech who repaired my airgun and he told me that he turned the 1/8″ inch striker hammer spring all the way CCW so that I’d have more power. He didn’t leave me a note with the airgun that he had made this adjustment to my gun so I thought I had a big problem at first. He said that he does it to all the .177 Marauders that he works on to give them more power. I don’t think a technician should make adjustments like that without being asked to do so, or he should at least include a note as to what’s been done. He says that he didn’t make any other adjustments. Anyway, can you tell me how I can get the striker hammer spring back to it’s original factory setting? Do I bring it all the way out CCW and then turn it CW for so many turns to get it back to it’s original setting, or do I turn it all the way CW, then bring it out CCW so many turns?

    Thank you,


    • Doug,

      I take it you don’t own a chronograph?

      Here is what you do. Use a piece of modeling clay or better yet duct seal. Shoot a certain pellet into it with the gun as tuned now.

      Then back out the adjustment screw two full turns and shoot the gun several times with pellets. Then shot another pellet into the medium (clay or duct seal). It shouldn’t penetrate as deeply.

      Now, see what kind of affect this setting has on the air pressure, per 10 shots.

      If it’s 200 psi, you’re done. If it’s more than 200 psi, it should still be less than 350 psi.

      You have now established parameters and will have to work with the screw setting until you get the pressure drop you are after. The clay/duct seal medium is to show you that you have not gone too far in the adjustments.


    • Doug this info may be to late for you. And on my part this is kind of sad because I usually keep statistics on my guns. But I looked back through my stuff and nothing on the stock settings of the Marauders. And this is my main airguns that I shoot. All kinds of other settings but nothing stock.

      But I do know the full amount of turns you can get on the striker is 12 revolutions which is what the manual says. So I bet that setting is in the middle for the stock adjustment.

      If you go counter clockwise till the striker adjustment stops then back 6 turns clockwise I bet you will be pretty close to back where the factory setting was at. This is just a guess. I do know though that the longer the stroke the more air the gun will use. So if you do adjust to the 6 turns and start going counter clockwise more turns you will get more power and less shots per fill.

      Don’t know if this helps any.
      But wonder to my self why I didn’t write down the stock settings. 🙁

      • Hi,

        This is what I found out on the internet, and through Crosman customer service about the factory settings for the .177 Benjamin Marauder:

        There really is no “exact” when it comes to the Marauder settings. Every gun has a bit of it’s
        own personality and we start at a fixed point then tune each one to get the required performance.

        Hammer Spring (Hammer Spring Pre-load Adjuster): 3 turns in clockwise from 0 (0 is all the way out counterclockwise)

        Stroke Adjustment (Adjusting The Striker or Hammer Stroke): 2 turns in clockwise from 0 (0 is all the way out counterclockwise)

        Transfer Port Adjustment (Valve Metering Screw): ~2.25 turns out counterclockwise from bottom (bottom is all the way in clockwise)
        (each valve is flow tested with a meter and adjusted to meet required flow)

        I’ve yet to try it, but will soon.


  13. Hi B.B.,

    So, there’s no exact, “this many turns CCW, followed by this many turns CW”? Just do it by feel? I would think that Crosman would have a precise number of turns before the gun is shipped with it’s factory settings. No?


    • Doug,

      No doubt they do have a specific number of turns. And that gives each rifle a different velocity, though it’s in the same ballpark for all of them.

      But I don’t know what it is and you don’t need it, if you do it that way I mentioned. A chronograph would easiest way to determine this.

      But my way works.


  14. BB,

    I want to thank you for doing this subject. Looking forward to more of this.

    The scopes I have bought (or have come with the guns) don’t go into much detail about adjustment. I think the manufacturers assume the buyer already knows all about this stuff.

    Then, when mounted to springers that actually break scopes while the gun is breaking in, it really poses a problem. I’ve had a couple of really harsh springers break scopes when new. I usually spend a lot of time and pellets trying to determine if the scope is broken or just out of adjustment. What usually happens then is I’ll buy a replacement scope and put the original in a drawer. Some time later I’ll take the scope back out and try it on another gun. If I still can’t get it to work, then it gets discarded. I gave one to a fellow worker to use as a spotting scope on his kid’s telescope.

    I try to buy scopes that are better quality than the ones that were broken. Generally, I’ll try shimming as a last resort.

    I didn’t know that many scopes use only one spring. Just figured here were two springs in there for vertical and horizontal adjustment.

    When trying to center the scope by backing the adjusting knobs to full travel (in or out), is there a danger of damaging the scope by doing so?

    And is there a standardized direction to turn them for up/down, left/right?

    A friend told me that when using a variable power scope, changing the magnification adjustment will throw the scope off center. Is that true? If so, why?

    I would like to see you go deeper into this subject.


    • Les,

      A lot of good questions.

      No, there should be no danger in running the adjustment out to the end of either direction.

      Some scopes change zero with power changes — others don’t. I depends on where the reticle is located in the optics package.

      The standard direction for scope adjustments is clockwise is down and left. Certain German and Chinese scopes are backwards from this, but they are the exceptions.


  15. B.B.,

    Another potential issue with scopes has to do with harsh firing springer’s. Some screws can shake loose and fall off.

    The scope on my friends springer, the one that went from shooting well to eventually not grouping at all, started to come apart at the knobs. I’ve not had this problem with any of my scopes. He bought a CenterPoint Scope, and the tiny screws that hold the adjustment knobs started to fall off, so some were lost.

    A couple things about this particular gun, and it’s mishandling. It was cleaned after every use with gun solvent. When I checked the muzzle, I found that the space between the actual muzzle and the muzzle-break containing the front sight was full of gunk. I believe that pellets were repeatedly hitting this gunk.

    As it turns out, when I first solicited advice regarding this gun and why it suddenly lost all accuracy, Vince hit it on the nose. Vince suggested that the gun was not being cocked properly. I never said anything about this, but as it turned out my friend was in fact cocking it wrong, and had plenty of bruises on his arms to prove it. In any case, the rifle is apparently ruined.

    So one lesson from this is that IF you clean your air-rifle often, check that space between the end of the barrels muzzle and any kind of muzzle-break or front sight. Gunk might collect there.


  16. Greetings B.B. and Air friends. Boy, does this blog hit home with me. My first really good gun was Weihrauch HW97 in .22 cal. Needing a scope, I was recommended a Hawke Airmax 4x12x40. I was also sold a cheap pair of scope mounts. After mounting the scope, and sighting in on my 7.5 meter indoor range, I found I was shooting 3 inches low. So, I cranked and cranked all the way to where the adjustment stopped. Still half an inch low, and my great half in. one hole group I began with had now opened up to a ragged 3 inches. I had no clue as to what was going on. After all, the HW97 is an under leaver, and didn’t show the massive droop my Norica .22 cal break barrel had. After some googling , I found out about shimming the rear mount. This put me on the bulls eye, but did nothing for what was happening to the erector tube. I had just discovered B.B.’s daily blog, but was such a newbie, I thought I would be told to stop waisting space with dumb questions if I wrote about my problem. To shorten an already long story, after finding I had to lower my scope when I started shooting longer distances outside, things began to make sense. And I did start writing in with dumb questions, and was treated with kindness and respect.
    All eventually worked out when my dealer brought in some adjustable one piece scope mounts. Apparently, I wasn’t the only one with this problem. I think, as others have indicated, we all need a refresher coarse in the fundamentals. Because sometimes the fundamentals give us or biggest grief.
    Caio Titus

    • Titus

      I love to read dumb questions. They are the only ones I have any chance of answering correctly! 😉

      In all seriousness, every hobby and sport is supposedly all about recruiting new blood into the game. The more the merrier. Yet the more experienced players make it hard by speaking in jargon and acronyms. When you are new to something you always feel tentative, and afraid you are going to ask something so basic, you will mark yourself as a simpleton for the rest of time. So you hold off asking about what you need to know, and stay in the dark. The thing is, we are all there at some point in our lives. The best thing we can do is to remember that, and to treat earnest and respectful new airgunners with respect, and help them along their airgunning journey to nirvana. That is why the Pyramyd AIR Blog is so great compared to many other airgun sites. So many knowledgeable people, and not a jerk in the bunch (except for me).

    • Titus,

      Now, THAT is a story I can use! An underlever with droop. People just don’t believe things like that exist.

      Thanks for sharing this story with us. You cemented my resolve to do more of these fundamental reports.


  17. There is mechanical centering of the erector tube and optical centering of same.

    Re the mechanical version, let’s say windage is already leftward to begin with. Now you cycle the elevation all the way up, then down, then halfway back towards center. Because the erector was already cramped left, you do not get the full range of elevation and do not get back exactly to middle. Now do the windage; at least you are assured the elevation is close to center. Now repeat both and I claim you are pretty close to exactly mechanically centered.

    Here’s my problem having done this on my two mid-range priced scopes. If I now do an optical centering, the erectors are no longer near their mechanical centers. 🙁 So I give up on passing both tests simultaneously.


    • John,

      Not necessary nor is it likely that your scope will “pass both tests simultaneously.”

      Mechanical centering is first about knowing where your poa vs. poi is and trying through shimming, adjustable mounts and/or barrel bending to get poa & poi close. Mechanical centering is secondly about preserving full range of adjustment for windage and elevation.

      Optical centering is about minimizing windage variations while shooting at all distances. You never touch your windage adjustment on your scope after optically centering or you’ve wasted your effort.

      Two different methods that have two different goals.


      • Kevin,

        Nothing I’ve red regarding optical centering has mentioned windage so I need more education on that.

        I’ve seen two optical centering procedures discussed (caveat – this was on the internet so one must read between the lines, keep tongue firmly implanted in cheek, like when reading what i’m writing here). Both methods done with AO (if exist) maxed out to infinity; magnification adjustment (if exist) maxed out…?…hmm?

        One optical centering procedure involves standing the scope on a mirror and adjusting turrets to align the actual crosshairs with their reflection. This mirror method makes no sense to me since it depends on the object lens beauty ring (not to mention the objective lens itself) lying in planes exactly perpendicular to the erector tube axis; otherwise a waste of time, imo.

        The other procedure involves rotating the scope in “loose” rings while adjusting turrets until crosshairs intersection remains stationary rather than following a circular path. Again here, the more symmetrical cylindrical geometric linearity between scope components, the better i would think and sounds expensive.

        So i’m not familiar with what You mean by “optical centering” in this context; would love to know more.


        • John,

          Yes, your two methods of optically centering a scope work. The mirror method does work (out to the 100 yards I’ve shot with airguns) but you need good light and a way to EVENLY suspend the objective of your scope above the mirror. Rotating a scope in “loose rings” or uneven “V”cuts in a cardboard box produce and slop in you “loose rings” allow produce equal errors in your attempt at optical centering your scope. If you only shoot out to 20-30 yards you probably won’t notice the differances. If you shoot out to 100 yards or more they can be significant.

          I’ve used proper scope rings (1″ or 30mm) mounted on a 2″ X 6″ clamped on my shooting bench to rotate scopes during the optical centering process. I now use the mirror method. I don’t do this for every scope but it’s a must for those scopes that will be on airguns expected to shoot at various distances out to 100 yards.

          As stated above the purpose of optically centering, no matter which method you prefer or prove satisfactory to yourself, is to minimize windage errors at most distances. Adjusting for elevation whether you click or holdunder or holdover doesn’t matter.

          In my experience most airgunners shoot at one distance so this doesn’t matter. A few airgunners shoot at 2 or 3 marginally different distances (10 meters, 20 yards and 50 yards) and an optical centered scope for them doesn’t matter much. At 50 yards they learn that they must (for some strange reason LOL!) hold off a half inch to the left (or maybe right) even when there isn’t any wind.

          A much bigger issue in my opinion, having shot with lots of airgunners at my hosted events, is parallax. It’s a rare shooter that knows how to dial out parallax and for airgunners that demand gnats accuracy at multiple distances even most seasoned firearm shooters are oblivious to this critical component in the equation achieving ultimate accuracy in shooting airguns (especially at long distance).


          • Kevin,

            THANK YOU for that explanation of optically centering a scope with a mirror. I have tried and tried using different mirrors and scopes and light sources but could never see the darn reticle! Now you point out that the scope should not be resting on the mirror but suspended slightly above it! Boy do I feel stupid!

            I never bothered to optically center a scope after failing the above test but always centered the scope in it’s physical adjustment range. That test I passed!

            Here’s one for you and Victor, you’ll roll your eyes on this. As Victor knows, I now shoot a rimfire in 25 yard bullseye competition. I have been improving especially with Victor’s help (marvelous long distance coach, guys) but the last three competitions, it seemed I was going backwards – scores getting worse and barely hitting the black. I have a red dot mounted on my High Standard Victor. Then this blog came out and it hit me, when was the last time I checked the screws on the Red Dot? Well they were all nice and tight but the adjustment for the type of dot (this Bushnell Pro I’m using has a choice of 5 different dots), had rotated between two of the choices, probably from putting it in an taking it out of my case!

            Now I have to get to the range Sunday to see if this was the problem! Thanks to you, BB, you’ve solved another problem. ALWAYS CHECK YOUR ADJUSTMENTS WHEN YOU UNCASE YOUR GUN!

            Fred DPRoNJ

      • Optical centering is about minimizing windage variations while shooting at all distances. You never touch your windage adjustment on your scope after optically centering or you’ve wasted your effort.

        You don’t have my Marlin/Glenfield 60c…

        The barrel (and stock inletting) have a distinct offset toward the left, relative to the receiver. To get a scope aligned with the barrel would require a scope mount where the rear mount sticks out the right side of the receiver. In exaggeration, a top down view is:


        I’ve shimmed the scope with (hold your breath) Dr. Scholls adhesive pads to reduce the offset, but the sight picture is still a triangle — not only does one have to adjust the elevation for distance changes, but the windage for distance changes.

        As for mechanically centering the reticle — fit the rifle into a vise or other shooting stand, leave the rings very loose.Sight some gridded target and note where the cross hairs are. Rotate the scope 180 degrees. Note where the cross hairs are now — adjust to take out half the difference. Repeat as needed to refine.

        Then do the same for the windage adjustment.

  18. I’ve never had issues with scopes but add me to the list of those who’d like a follow-up. Maybe you could address parallax, how it affects POI at various ranges, and why it’s set at 100 yards on so many scopes when most airguns aren’t going to be used at that distance?

    • Mr. Dongle

      The 100 yard fixed parallax scopes are not made specifically for airgunning. They are firearm scopes that are sold to the airgun market.

      There are at least two things wrong with this. First, as you mentioned is the fixed parallax. 100 yards is much too far for almost all airguns, and for almost all airgunners. (Harry from Oz not withstanding) Even if it were fixed at a more reasonable range, it is still fixed. An adjustable objective not only gives a clearer sight picture, but allows for a degree of range estimation (especially if you have taped the objective bell or wheel and marked at known distances) which can give the shooter an idea of how much to holdover or adjust the elevation turret to account for drop at a given distance.

      The second problem is that scopes not made specifically for airguns are less durable. That may sound counter intuitive, but powder burners recoil in one direction only: backward. Springer airguns recoil first backward, then forward. The abrupt change in direction plays hell with scopes. This is why magnum springers often break scopes, and why quality scopes made for the airgun market are made with more durability in mind.

      Personally I will not buy a scope without AO, not that I am the ideal to be imitated.

      • SL,

        The 100-yd parallax scopes on Pyramyd Air’s site are mostly bought by airsoft skirmishers. I can’t understand that since I don’t think most airsoft guns can shoot 100 yards. If they can, I don’t think they have any hope of being accuracte. However, Pyramyd AIR had a number of 100-yd parallax scopes, and we found that airsoft shooters were buying them. These are almost always low-magnification scopes, and that seems to make less of a difference than if they were high-magnification scopes.


        • Edith

          That is kind of weird. I am thinking that the airsoft shooters are buying these scopes because they are low cost, but who knows? As Kevin mentioned, some fixed parallax scopes can be adjusted by removing the front trim ring and turning the ring that contains the front lens. So maybe that is what they are doing. I just worry about this procedure, because good scopes are charged with nitrogen to eliminate fogging/condensation. I would think that fiddling with the lens might release some of the gas inside.

          It makes sense that the airsofters would use lower magnification scopes because higher magnification greatly increases the effect of parallax error, ie the target would be increasingly blurry as the distance decreased from 100 yards under high magnification. Also adjustable magnification adds to the cost of a scope, hence fixed parallax, fixed magnification.

          Regarding accuracy with an airsoft gun at 100 yards, I think the only target you could reliably hit at that distance would be the ground. But I know nothing about airsoft, so my comments aren’t worth the ink they are not printed on.

    • dangerdongle,

      Slinging Lead gave a great answer In My Humble Opinion.

      Many 100 yard parallax scopes can be adjusted, BY YOU, to less than 100 yards. The problem is that when you dial the parallax to a lessor (or greater yardage) they are only parallax free at that distance and that distance only. Not a bad thing it just is what it is.

      I have many scopes WITHOUT AO that are mounted on airguns that have been adjusted to 20 or 30 yards. Why? They’re on airguns I use for hunting and want quick acquisition of target without necessity of messing with AO. Yes, the target gets blurry at distances shorter and longer than where I have adjusted the parallax but the trade off is worth it to me. Let me add that my scopes are fixed magnification which in my experience hold up better ON SPRINGERS than variable magnification scopes.


      • Kevin,

        Lots of more powerful scopes come with fix parallax scopes. Some (more correctly, I think) recommend that you not install a scope until after some break-in period, while others are quick install a more complex scope right away. I’ve had a couple powerful springer’s that physically destroyed airgun rated scopes. As you say, fixed parallax scopes are better suited for some rifles, so for one of my rifles that’s all I’ll use on it.

        My most conservative advice for someone who buys a magnum springer is that they first break the gun in with iron sights, and then further break it in with the scope that came with the rifle. Then if they feel confident about this rifle’s treatment of scopes, try something more complicated.


      • Thanks guys! I assumed ( I know, I know) the scopes at PA for instance _were_ strictly airgun scopes, considering most of the Nikons, Leupolds and the like that people buy for firearms generally do not have AO or even mention what parallax is set at!

  19. I luv the side parallax scopes with the big diameter adjusting wheels.

    The way I look at is that it is an adjustable built in range finder on your scope. Rotate the wheel till the object comes into focus ( the bigger wheels work great because it gives you a finer focus adjustment ). Look at the markings on the wheel and see what the dot or arrow lines up at for how many yards out you are focused to.

    Then if you know what your hold over or hold under is by what mildot to use on your scope for a given range. All you do is focus the side wheel parallax on your target and look what yardage the wheel shows. It will then give you the estimated range your target is at.
    Oh and you can use the scopes with the front adjustable parallax but you usually have to move your eyes way away from the cross hairs so you can see the yardage up on the front of the scope then go back and find your target through the scope again.So I prefer the side wheel scopes.

    I have a laser range finder that I use to compare the readings of the parallax on the scope on the gun and see if they come up with a similar reading to each other.
    And then if you use something like the Chair Gun Pro ballistic calculator program. And get your recticle maps of the mildot hold overs for your pellets,fps and other neat things you can input into the program. Target sighting at different ranges becomes very quick.
    It is pretty amazing how quick you can focus your target,look at the range on your wheel,do your hold over for the range it says and shoot. And be pretty accurate hitting your target.

    And there is only one airgun that I thought I was having problems with as far as shimming for elevation was concerned and that was my Diana 54 Air king in .177 cal.
    Turned out (not needing to be shimmed). But actually needed a little taller scope mount.
    Didn’t touch the scope adjustments. Just swapped to the taller mounts and did some shooting.
    Guess what. Gun was shooting a couple of inches high at the same 50 yrds that the other mounts where always about 2 inches low.

    That is one of the dimensions you have to measure for the Chair Gun program is scope height from the center of the barrel diameter to the center of the scope diameter. Try changing that on the program and see how much it changes the pellet path.

    They have a free program you can down load on the Hawke website. If you don’t actually use it for shooting it is still fun to input different info and see how it effects the pellet path.

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