Home Blog  
Ammo Advanced airgun diagnostics: Part 1

Advanced airgun diagnostics: Part 1

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

I don’t know about the rest of you, but this blog is teaching me things. I’m learning a lot more things by doing all these little tests and experiments than I ever learned by reading about airguns. Of course, that’s partly because there aren’t that many good books around, but it’s more because of the excellent discussions we have here. And more often than not, something really special comes from all this study.

Yesterday, I was finishing an article for my monthly column in Shotgun News when I happened to spot something interesting. I was writing about the Chinese KL-3B Fast Deer sidelever spring-piston air rifle and I showed two targets — one shot with RWS Hobby pellets at 10 meters and another shot with the same pellet at 25 yards. The 10-shot group at 10 meters measured 0.38 inches between centers, and the 10-shot group of the same pellet that was shot at 25 yards measured 1.918 inches. That was certainly a huge increase for just moving the target 14 yards farther! But it was more than that. I had seen something similar recently — something that really stuck in my mind.

Fast Deer sidelever air rifle right
Fast Deer sidelever rifle has a quality look, but the accuracy falls off fast after 10 meters.

Fast Deer sidelever air rifle RWS Hobby group
At 10 meters, the Fast Deer put 10 Hobbys into 0.38 inches.

Fast Deer sidelever air rifle Hobby group
But at 25 yards, another 10 Hobbys went into 1.918 inches.

Then I wrote something in the column that jogged my memory. I said the Fast Deer was acting like it was a smoothbore because it shot great at 10 meters but lousy at 25 yards. That was just how the Diana model 25 smoothbore had shot when I tested it last year! And that’s when it hit me. As I remembered it, it was performing EXACTLY like the Diana model 25 smoothbore!

Diana 25 smoothbore
The 1940 Diana model 25 smoothbore performed exactly like the Fast Deer air rifle.

So I looked it up, and I was right. With JSB Exact RS pellets the Diana 25 put 10 into 0.337 inches at 10 meters, and at 25 yards it put the same JSB Exact RS pellets into 2.421 inches after I played with the seating to find the best place.

Diana 25 smoothbore JSB Exact RS deep-seated group
At 10 meters, the Diana 25 smoothbore put 10 JSB Exact RS pellets into 0.337 inches.

Diana 25 smoothbore JSB Exact RS deep-seated group1 25 yards
But at 25 yards, the best the Diana 25 could do with 10 JSB Exact RS pellets was 2.421 inches.

Learning has occurred! I now know that I’m getting the same results from a gun with a rifled bore as I got from one that is a smoothbore. Or, to put it another way, the rifled gun shoots like the pellets aren’t being stabilized by the rifling. It shoots like a smoothbore.

Is the Fast Deer even rifled?
Then I wondered if the Fast Deer is really rifled. So, I ran 2 different pellets down the bore from muzzle to breech — have to go that way because the barrel is fixed. Both pellets (RWS Hobby and an old Tech Force Chinese pellet) showed good engraving around the bases of their skirts, but only one showed any contact with the pellet head. Unfortunately, the RWS Hobby that I’d used when testing the rifle did not have any marks on its head. Instead, it was the domed Tech Force pellet made years ago that had engraving. However, I never shot the Chinese pellet when testing the gun for accuracy. Pyramyd AIR used to carry them, but they no longer do. The point is, they may solve the longer-range accuracy problem. If they don’t, I will look around for another fat .177 pellet that will.

So what we have is a Part 6 test coming up for the Fast Deer rifle. I said I would scope it and shoot it at 25 yards for Part 6, but if it doesn’t shoot accurately with open sights at 25 yards, that seems like a big waste of time.

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.

45 thoughts on “Advanced airgun diagnostics: Part 1”

  1. BB,
    Definitely, worth a look! I think it may have more to do with variance in the attitude of the pellet as it exits the muzzle than complete lack of spin, but bigger pellets should work better either way. I also think you will be researching an aspect of one of the most fundamental and most annoying phenomena pellet shooters encounter: “Pellet Pickiness”. I suspect head size may play a large role in that.

  2. It sure would be nice to come up with some kind of rule of thumb to get the right pellet for your gun.

    And when you think you got something figured out some sort of surprise happens and it makes you think again.

    That’s why the swaged bullet/pellet articles interest me. I think that when you swage it gives you a idea how the pellet fit and shape and weight make a difference when you try different sizes. Along with the air pressure tune and the type of barrel you have.

    Maybe swaging a bullet/pellet may not find the most accurate one from your gun. But it may show you what works better or not as well.

    Then you could possibly look at the design when you are deciding what type of pellet to try that is already being produced by the manufacturers.
    And that way have a little better idea of what to look for maybe ???

    All I know is I sure have gave alot of pellets away through time for other people to try. They thought some were fine and some not as good also.

    I think I’m to picky with accuracy sometimes but that’s why I shoot mostly air guns. All I know is when you get things right they are some accurate guns.

    • You’re not too picky. I sold my CFX because I couldn’t get a satisfying group at 50 yards with it. It would also shift POI with an almost imperceptible bit of thumb pressure.

      What you are going to find is every air gun is going to surprise you when it comes to pellet preference. My Talon SS with a 26 inch .177 HW barrel actually prefers Eun Jins over any other pellet. Go figure. They are probably the lowest quality pellet made right now that is readily available, but those big, heavy chunks of lead produce the tightest groups out of that set up.

      • RR
        I remember you saying that about the Eun Jin pellets before shooting from that gun.

        That’s what I mean about when sometimes I get surprised by how a pellet performs great in one gun and just terrible in another.

        And if I remember right the Talon you are talking about was a hot shooter.
        I would definitely be happy with that gun if I owned it.

          • BB
            I bet that gun is making some serious fpe. And again if I remember right it was shooting a nice number of fps.

            Did the flat trajectory seem to make some kind of difference in accuracy ?

              • BB
                Oh Ok. Yep the flatter trajectory does work better for that.

                I use hold over when I shoot.
                Four of the PCP guns I shoot all the time each has a different hold over I have to use.

                • Actually it did better when I slowed it down a good bit. When I got it, the top of the curve was a fill pressure of 1800 psi and Eun Jins were ripping down range at about 1100 fps!

                  When I tuned it down to where the Eun Jins were at 800 fps it would group below 1 inch at 50 yards. The main problem is that the valve is a high flow valve and everything else goes supersonic.

                  I am seriously thinking of selling this barrel and getting an 18 inch .22 barrel for it. That will be much better suited to this valve setup.

  3. As BG_Farmer suspects, I know for a fact head size can indeed play a large role in accuracy. My CFX did not care for H&N Field Target Trophies in 4.51mm head and would at best produce quarter size groups at 25 yards, but when I fed it the 4.52mm head it would produce groups that would literally hide under a dime. It really liked pellets to fit snug.

    But if my memory serves me correct (I wouldn’t bet my life on it), that is not a hard and fast rule. I am sure BB can show several tests where the opposite is true.

  4. Feinwerk,B.B.,
    Did a little tweaking as you suggested and the P17 is now cocking but only when the right handle grip is off. There is roughing of the plastic where the sear spring makes contact with the handle grip when closed. I don’t think this is supposed to happen?? Any suggestions to correct this??

  5. B.B.,

    A bit off-topic, but then again, maybe not too far off.

    This report and the one you did about swaged bullets has me recalling the Beeman Pell-Sizer. That product’s packaging claimed that it has “compound tapers for careful, gradual sizing without swaging.” Does that mean that it reshapes the skirt only? Or, is that more likely marketing hype?

    Also, you have any experience with the device and if so, what is your opinion of it?



    • Michael
      I was kind of thinking the same when I made the comment above about swaging.

      I would be interested also if anybody has ever tryed using the pellet sizer and what the actual results were and what dimensions it changes on the pellet.

      • I have used a Beeman Pell Sizer back in the 80’s when I bought my Deluxe R-10. I used mostly Beeman pellets back then and the most accurate pellet was the Beeman RamJet .177. I shot Silver Jets, Crow Magnums, Silver Arrows, Silver Ace and Kodiak Match. I shot over a chronograph using unsized and sized pellets using .1785 & .1780 dies. The results were interesting. The unsized pellets shot the fastest. The .1785 sized pellets shot the most accurate but slower. I didn’t finish with the .1780 as the first couple pellets showed no better results. Surprising was that the RamJet got faster and more accurate and I immediately sized the remaining pellets.
        Currently I shoot H&N pellets and sizing them can yield a less or more accurate pellet and always a slower pellet , in my old R-10.

    • Michael,
      I have this thing called a TED that I think came from Beeman. It came to me in a package deal and I really haven’t messed with it. I think at the time when they were popular the pellets available where not made as consistent as what is available now but that is just a guess maybe some one can shed more light on this device.

      • I figured that a precisely choked barrel would improve accuracy, but not all barrels are choked with vintage pellet guns and, I imagine, not with lower-end pellet guns of today, either.

        The Marauder has a choked barrel and Lothar Walther barrels are choked, I believe, but if they make such a difference (and they clearly do), wouldn’t every airgun buyer want only airguns that have choked barrels?

        I’m probably sounding goofy, but any pellet gun that isn’t accurate holds no great interest for me. Why would an inaccurate airgun hold any interest for anyone? Even plinkers like me want to hit what we’re plinking at. As long as the extra cost isn’t crazy high, wouldn’t everyone insist that a pellet gun have/do everything, including having a choked barrel, to make it as accurate as it can be?

        Y’know, I AM being goofy. I’m asking those questions in a world in which I know there are people out there who think a spring-powered pellet gun exists that they can hunt deer with.


        • Michael,

          There is nothing goofy about wanting accuracy in my book.

          Yes, many PCP barrels are choked. Not all Lothar Walther barrels for PCPs are choked. The buyer has to specify it and pay for it.

          Choking assures that all pellet leave the bore the same size. That means they all seal the bore the same. A spring gun doesn’t need a choke since it blows the skirt into the bore and sizes it at that time.


  6. I don’t know if this is relevant but for what it’s worth here are some of my experience with pellet testing.

    First I test for a precision rifle team so 10 meters is all they shoot and only use wad cutters. With high end rifles and pistols (anschutz,FWB, Walther) I will test different lot numbers with different head sizes at 60 feet (indoor range max.) that will hold a .100″ 10 shot group CTC for rifles (10.5 score on standard 10 meter target) and .150″ for pistols. Then I will order 2 or 3 sleeves (5,000 pellets per sleeve), enough for a season. From year to year they do not always end up being the same head diameter. With lower end rifles (Daisy 8XXs, Crossman Challengers) I do the same testing. A new one out of the box will rarely produce a group better than .250″ CTC but after a season of use it will normally shrink group size down bellow .200″. I have one Crossman Challenger with three seasons on it that did group .100″ last year and it will be interesting to see how it will do this year (I got the precision guns done but still need to do the sporter rifles we are just starting to get cranked up for this year).

    Now one thing that I have done is test R10s, Meisterkugelns, Hobbys and a few others from different shipments (so I assume different lots) and have found although very small repeatable group size differences.

    I probably shouldn’t submit this comment because it barely makes sense to me and I’m writing it. I bet Matt could have typed this and made sense of it in a fraction of the time!

    • caveman
      Totally makes sense. I found that out long ago about how the pellets will change by lot.

      I don’t competition shoot I just shoot for fun. Seems like every hobby I get into I get too serious and then end up stressed trying to get it right. And funny as it may sound it relaxes me when I shoot.

      But like I said, I like accuracy so one of the things I look for is a reasonably priced pellet that performs well.
      One of things I do when I find a pellet that works in one gun or even multiple guns.
      Is I will buy at least 4 to 8 tins of that pellet. And if I order more later on down the road I will not start shooting them until I have the last bunch of tins shot up.

      It works for me but maybe there is a better way of doing that also.

      Oh and what is the thing from Beeman that is called TED ?

      • GF1

        Watch how you order pellets. Those lot # changes can bite you. I have ordered four tins of pellets, but when I got them they had to come from a different die which was way too small.
        I have gotten tins that had a bad die too. Sometimes it’s better to order one tin, check them out, and if they are good then turn around and order a bunch more. You still could get burned by receiving pellets from different batches. Sometimes they will be about equal, and other times they could be a lot different.
        Always a crap shoot.


        • TT
          I know. That’s why I try not to go too crazy with how many I buy at time. And I don’t start shooting the next bunch till that bunch is done. Although I know some people say buying the bulk boxes of ammo is a good thing to do.

          I have finished 1 tin then shot the next 2 tins and they were the same but different than the first tin.
          Then shoot the 4th tin and be different than the other 3.

          But at least that way you can be aware of the change. And most of the time the change isn’t much.
          But I have shot one tin that would shoot higher than the other tin. And also some tins that shoot a little different left or right.

          I think the big thing is to know that kind of thing will happen and not to start messing with your gun or its sights. Again just being aware I think is a big help.

  7. After you’ve done all of your pellet head & skirt measurements ~ get your powder scale out & start weighing. Many time you won’t even find “ONE” that meets the weight marked on the container!

  8. When picking a pellet, a good first step is try one that is offered by the manufacturer of the air rifle. Such as, “RWS rifle, RWS pellet.

    If I remember right, BB said that!


  9. If I want to check the rifling on a gun I found this works quite well. First, as always make sure that the gun is unloaded. Never ever work on a gun that is loaded. That is for those that need to be told this. Second, get a nice bright flashlight. If the gun is a fixed barrel open the breech and shine that nice bright flashlight directly inside that breech trying to angle the light down the bore as best as you can. Then look down the muzzle. You will be able to see the rifling if it is present. This doesn’t necessarily tell you if it is working by spinning that pellet but you can see the rifling and any dirt in the barrel which tells you if the thing needs a cleaning. If all is well and the gun still isn’t able to hit a target smaller than a barn at 25 feet then I would assume one of two things is happening. Either I am doing something very wrong or that the gun just plain needs to be retired and scrapped for parts. If the gun just doesn’t shoot straight then it must be that the factory made a poor product or in the case of an older gun it has been shot to death and there’s not much you can do to fix a worn out gun. If it’s sloppy manufacturing it’s best to return the gun and get a replacement. In the case of anything made in China it’s practically a guarantee that it’s sloppy manufacturing and the replacement won’t be much better. I have discovered that no matter the product, china is incapable of making anything remotely like a quality product.

    I have a Ruger explorer here still in the box, never fired once. I took it out of the box to test fire it. When I broke that barrel open to cock it I got a face full of springs and other parts. It was the breech lock shattering when I opened the gun’s breech. So I pretty much bought a pre-broken gun. I checked and I found “Made in China” on the box. So I wasn’t very surprised.

  10. BB, I am curious as to why you picked the Fast Deer as the subject to write about for Shotgun News?
    Are they being imported again? That’s about the only reason I could come up with.

    I looked at the 25 yard target from the Fast Deer to see if the pellets were tumbling but they do not appear to be. I was surprised to see that neither 25 yard targets showed evidence of that.

    David Enoch

    • David,

      I do all sorts of gun for “Shotgun News.” I did an entire feature article on my Falke 90 underlever and they certainly are not available.

      “Shotgun News” has many articles about collectible firearms and airguns. They don’t just include things that can be bought today. They are very much the same today as “Guns & Ammo” was back in the 1950s and ’60s, before they became so commercial.


  11. Well, B.B. always said that shooting airguns is like shooting blackpowder. But that’s a pretty extreme difference even for airguns, especially when you’ve got airguns shooting well way past that. So do the better air rifles like the TX200 have more pronounced rifling or does the difference lie elsewhere.

    Slinging Lead, I didn’t misread what you said yesterday about the IZH61. I just totally used the wrong word. I put “low” when I meant to say “high.” It’s hard to correct things like that. 🙁


      • BB

        You know that’s funny what you said about what China does to make their tooling last longer. Another perfect example of why their quality is junk.

        They have tryed to out source parts we manufacture at work to China at various times in the past hoping to get the parts made cheaper.

        Well all I can say is every time they tryed it was a big fail. Parts got sent back to us for stupid things wrong with them. We had to rework them or scrap them and re run the orders they messed up.

        So yeah they sure saved money by letting them try to make them. Oh yeah, what about the extra cost of shipping us bad parts that they thought they did a wonderful job making.

        Sorry but just had to vent about that. You know give them jobs while we loose ours.

        That’s why I try to buy the American made guns. I should say also I have always liked the German and English guns along with the Turkish guns. And there is others I like I’m not thinking of right now too.

        But the send jobs to China thing kills me. Again sorry about venting. And I probably shouldn’t even post this. But here it goes.

  12. B.B.,

    I’m getting excited about Roanoke/Salem since your reports are always well photographed and you return with such interesting stories.

    I know this one will be different but be at ease since my thoughts and spirit and others thoughts and spirits will be with you.

    Please trade that R8 for something interesting.


  13. B.B. , we both have handled a lot of guns in our years[don’t care to touch the age part] but even though we used them and are very knowledgeably on them, we are never too old to learn something new every day . I read and look. your blogs open my eyes up, sometimes its a simple over looked thing . you do keep us on the look

Leave a Comment

Buy With Confidence

  • Free Shipping

    Get FREE shipping on qualifying orders! Any order $150+ with a shipping address in the contiguous US will receive the option for free ground shipping on items sold & shipped by Pyramyd AIR during checkout. Certain restrictions apply.

    Free shipping may not be combined with a coupon unless stated otherwise.

    View Shipping Info

  • Shipping Time Frame

    We work hard to get all orders placed by 12 pm EST out the door within 24 hours on weekdays because we know how excited you are to receive your order. Weekends and holiday shipping times will vary.

    During busy holidays, we step our efforts to ship all orders as fast as possible, but you may experience an additional 1-2 day delay before your order ships. This may also happen if you change your order during processing.

    View Shipping Times

  • Shipping Restrictions

    It's important to know that due to state and local laws, there are certain restrictions for various products. It's up to you to research and comply with the laws in your state, county, and city. If you live in a state or city where air guns are treated as firearms you may be able to take advantage of our FFL special program.

    U.S. federal law requires that all airsoft guns are sold with a 1/4-inch blaze orange muzzle or an orange flash hider to avoid the guns being mistaken for firearms.

    View Shipping Restrictions

  • Expert Service and Repair

    Get the most out of your equipment when you work with the expert technicians at Pyramyd AIR. With over 25 years of combined experience, we offer a range of comprehensive in-house services tailored to kickstart your next adventure.

    If you're picking up a new air gun, our team can test and tune the equipment before it leaves the warehouse. We can even set up an optic or other equipment so you can get out shooting without the hassle. For bowhunters, our certified master bow technicians provide services such as assembly, optics zeroing, and full equipment setup, which can maximize the potential of your purchase.

    By leveraging our expertise and precision, we ensure that your equipment is finely tuned to meet your specific needs and get you ready for your outdoor pursuits. So look out for our services when shopping for something new, and let our experts help you get the most from your outdoor adventures.

    View Service Info

  • Warranty Info

    Shop and purchase with confidence knowing that all of our air guns (except airsoft) are protected by a minimum 1-year manufacturer's warranty from the date of purchase unless otherwise noted on the product page.

    A warranty is provided by each manufacturer to ensure that your product is free of defect in both materials and workmanship.

    View Warranty Details

  • Exchanges / Refunds

    Didn't get what you wanted or have a problem? We understand that sometimes things aren't right and our team is serious about resolving these issues quickly. We can often help you fix small to medium issues over the phone or email.

    If you need to return an item please read our return policy.

    Learn About Returns

Get FREE shipping on qualifying orders! Any order $150+ with a shipping address in the contiguous US will receive the option for free ground shipping on items sold & shipped by Pyramyd AIR during checkout. Certain restrictions apply.

Free shipping may not be combined with a coupon unless stated otherwise.

View Shipping Info

Text JOIN to 91256 and get $10 OFF Your Next $50+ Order!

* By providing your number above, you agree to receive recurring autodialed marketing text msgs (e.g. cart reminders) to the mobile number used at opt-in from Pyramyd AIR on 91256. Reply with birthday MM/DD/YYYY to verify legal age of 18+ in order to receive texts. Consent is not a condition of purchase. Msg frequency may vary. Msg & data rates may apply. Reply HELP for help and STOP to cancel. See Terms and Conditions & Privacy Policy.