Diana 25 smoothbore pellet gun: Part 3

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

Part 1
Part 2

Diana 25 smoothbore
This Diana 25 smoothbore was made during World War II.

What a topic to follow a twist-rate report — one about a smoothbore! Today, we’ll look at the accuracy of the WW II-era Diana 25 smoothbore airgun. This is a play-day for me because this gun is so non-finicky and trouble-free. It’s the way I wish all airguns could be. Just load and shoot. No special handling beyond the basic artillery hold, and no need to treat it like it’s a vial of nitroglycerin.

Shoot from 10 meters
I decided to shoot from a rest at 10 meters just because this is a smoothbore, and I had no idea of what results we would get. I hoped it would hit the paper with all shots. That would be good enough. But nothing beats shooting, so that’s what I did.

JSB Exact RS
The first pellet I tried was the JSB Exact RS, which is a .177-caliber favorite of blog reader Kevin and has become one of mine, too. It seems to work in most airguns, and it’s often one of the very best pellets. So, how would it do in a smoothbore?

I shot off a rest with the artillery hold. My off hand was back touching the triggerguard, but the gun is not muzzle-heavy. The first shot landed below the center of the bull — but actually at the point of aim, if a bit off to the right. So, the rear sight elevator was pushed forward to raise the sight. I didn’t care if it was hitting the center of the bull or not, but I wanted to keep the shots mostly inside the large black bull of a 10-meter pistol target because I could see the holes when they were in the white and distracted me.

The first 10 shots were fired with the pellet seated flush with the breech face. And the group turned out better than I had expected, though about as good as several readers had indicated they get from their smoothbores. It may not look that good to you, but notice how narrow it is compared to the height? That’ll become important in a moment. This group measures 1.158 inches between centers.

Diana 25 smoothbore JSB Exact RS flush-seated group
Ten JSB RS pellets in 1.158 inches, center to center, at 10 meters. The lone shot in the white was the first sight-in shot and is not part of the group.

Next, I shot another 10 rounds of RS pellets, but this time I seated each pellet deep in the breech with the Air Venturi Pellet Pen and PellSet. As before, the pellets all landed in the black bull, so it wasn’t until I walked down to change the target that I saw the group. Imagine my surprise to see a 10-shot group that could just as easily have been shot with an expensive target rifle! Ten JSB RS pellets went into a group that measured 0.337 inches between centers.

Diana 25 smoothbore JSB Exact RS deep-seated group
Ten JSB RS pellets seated deep in the breech made this 0.337-inch group at 10 meters. This is amazing for a smoothbore!.

You might shoot 5 shots some time and luck out like that, but 10 shots tell the truth. This airgun is very accurate at 10 meters, even though it’s a smoothbore. And it takes deep-seating the pellets to do it — at least with the JSB RS pellet. Now, I was curious. Would the two other test pellets show similar results?

Beeman Devastator
The second pellet I tried is one I don’t shoot a lot, but after it did so well in the Velocity versus vibration accuracy test I did a year ago, it has moved into the category of pellets I like to try when the circumstances are unusual. The Beeman Devastator is a hollowpoint that acts like a wadcutter at the same time. And a smoothbore is definitely unusual. The first 10 flush-seated pellets went into a group measuring 1.948 inches between centers. Not very good and more like what I’d been expecting from this airgun.

Diana 25 smoothbore Beeman Devastator flush-seated group
Ten Beeman Devastators didn’t group too well when seated flush with the breech. Group size is 1.948 inches between centers.

Now, it was time to shoot 10 Devastators that were seated deep in the breech. Would they also tighten up?

Well — yes and no. The 10-shot group of deep-seated Devastators measures 1.982 inches between centers, which is a little larger than the group of flush-seated pellets. However, 8 of those pellets did group into 0.691 inches. I would say that the deep-seating method still looks promising at this point.

Diana 25 smoothbore Beeman Devastator deep-seated group
Ten deep-seated Beeman Devastators made a group of 1.982 inches between centers, but 8 of those were in 0.691 inches. Deep-seating still looks good.

RWS Superdome
The final pellet I tried was that universal favorite — the RWS Superdome. The first group of flush-seated pellets was not that large, at 1.156 inches. If the deep-seating method held true for this pellet as well, it might beat the tight RS group when seated deep.

Diana 25 smoothbore RWS Superdome flush-seated group
Ten RWS Superdomes went into 1.156 inches at 10 meters. This is the best flush-seated group thus far.

A happy accident
As I was shooting the next group of Superdomes, I forgot to seat the second pellet deep and had to stop shooting the target. But the result on target was so dramatic that I photographed it, so you could see what happened. The deep-seated pellet is the high one and the flush-seated pellet is the low one. That shows more clearly than anything how deep-seating affects the shot.

Diana 25 smoothbore RWS Superdome mistake
The deep-seated pellet went high and the flush-seated pellet went low. This shows the dramatic difference deep-seating makes.

Deep-seated Superdomes
Then I got serious again and shot 10 rounds of Superdomes seated deep. They made a group sized 1.047 inches. While that’s only a little better than the same pellets seated flush, notice that these shots are centered in the bull much better. Not that I’m looking for that, but it’s a nice side benefit.

Diana 25 smoothbore RWS Superdome deep-seated group
Ten deep-seated RWS Superdomes went into 1.047 inches at 10 meters. It’s better than the flush-seated pellets.

What have we learned?
The first thing this test has taught us is that a smoothbore airgun isn’t that much of a disadvantage at 10 meters. I think the results of the RS pellets definitely call for another test of this airgun at 25 yards.

The next thing I learned is that deep-seating the pellets seems to improve their accuracy. Some improved more than others, but every pellet seems to have done better with deep-seating.

The last thing is that all of this shooting, all 63 shots, were fired with simple open sights. After some of the trauma you’ve witnessed me undergo in recent weeks to get some air rifles to group, this little Diana 25 seems to have breezed past all the big-name guns and taken the lead. I think that says a lot about what power levels are best for spring-piston air rifles.

78 thoughts on “Diana 25 smoothbore pellet gun: Part 3”

  1. Morning all. Well that is an interesting difference in height between the seated and flush pellets, which would make me self think there is a difference in velocities as you have demonstrated on previous blogs. I am assuming that the higher shot is the higher velocity, but i could be wrong as i get confused over power curves this early in the morning.

    best wishes, wing commander Sir Nigel Tetlington-Smythe

    • Nigel,

      A lower velocity shot will usually impact high on the target at short range like this. It is traveling in the barrel for a longer time while the muzzle is reaching up, so it leaves the barrel at a slightly higher elevation than the faster pellet. A long range target will show the slower pellet as lower due to the trajectory.

      You have a heck of a long signature. Care to fill us in? 🙂


      • Thanks Dave, now the day has come on and i am now not so bleary eyed i realise that my earlier assumption was incorrect. 10 yards i should imagine is below the point at where the pellet 1st crosses the line of sight, would i be correct in assuming that all shots taken beyond this distance would then strike higher with more velocity behind the pellet? I can now see the mistake in my thinking, and appreciate your help in pointing this out for me.

        As for the rather large signature i always finish off with? Well that came about from my wife changing my facebook name one time years ago and i rather liked the sound of it, as it’s pretty much my name without all the titles. She has even sent me presents through the post under that name, i know it’s a bit silly, but it’s fun. Take care now Dave.


        best wishes, wing commander Sir Nigel Tetlington-Smythe

  2. I see PA no longer has the AA Falcons. I guess I am going to have to get some of these Exact RS if they get them back in stock. if I am not mistaken, they are the same pellet.

    I have seriously been thinking of a R7. A low powered sproinger would be fun to have around. Maybe we will see what turns up at the show this year.

    • RidgeRunner,

      Shame that PA doesn’t have the Air Arms Falcon pellets. Seems everyone is having a hard time keeping JSB pellets in stock.

      JSB makes the air arms falcon pellets and their specs are similar to the JSB RS pellets and both look similar. They don’t perform the same. I was told that one of the reasons for this is that Air Arms paid for/supplied?? a different die for their pellets. Some of my airguns prefer the air arms falcons over the jsb rs pellets and others prefer the rs over the falcons.

      Would encourage you to try both the rs and falcons in your guns for these reasons.


  3. B.B.

    When you talk about deep seating here, just how far ?
    Was it just barely enough to get the skirt into the bore, or did you really stuff them down in there ?

  4. Question: Does deep seating a pellet reduce force of the piston slamming more so than a flush pellet? For instance, I use a 10.5 grain pellet in my 1,200 fps gas piston rifle to reduce the violence of the piston as it slams home versus a 7.9 grain pellet. Not sure that even helps, but seems like it should. So, again, would deep seating a pellet do the same thing? Second question: does deep seating affect velocity? If question number one is “yes”, then perhaps question number two is also “yes”. Confusedly yours, SE MN AIRGUNNER

    • SE MN,

      Deep-seating reduces the friction and actuall metal distortion that has to happen when the piston slams home, so it doesn’t reduce the slamming — it increases it. Less resistance for the piston.

      Here is a report I wrote about this:


      It appears that I never investigated this further, except within reports on specific guns, and I seem to have done a lot of that. I got sick soon after this report which is probably why I never came back to it.

      As I recall, deep-seating improves velocity on a few very low-powered spring guns, but on most of them it decreases power. I doesn’t seem to work very well on high-powered guns like yours.


      • Anecdotally, I can tell you that my Nitro Venom Dusk .177 is more accurate with flush seating. Your comment supports what I suspected. It also seemed they would hit with less “thump” further confirmed by your comment. I was only hoping to reduce the violence, not for accuracy purposes, but protect my scopes. The scope that came with the gun soon lost its zero. Bought a Gamo “shock proof” scope, that one also lost its zero after a couple thousand shots. Now I have a Leapers Bug Buster that seems to have lost its zero, again, after about 2 thousand shots. I’m convinced it is the severe violence of the piston. The gun can get sub 1 inch groups at 25 yards (I know very mediocre), but that is a lot easier to achieve when you have confidence in your scope!!!! 🙂

  5. To me these rifles are what springer should/must be.
    I don’t want hard to shoot, vibrating, magnum power out of a springer.
    I want the fun factor, I want the easy to shoot and hit what you aim at all day long in your backyard.
    I want small Slavias, Dianas, Broncos and IZH 60/61 to name a few.

    This to me is the perfect springer rifle. The essence of springer rifles.
    I have a few of them and I do a rotation of these nice rifles that I keep by the back door with a can of pellets so whenever I have a minute, when using the BBQ or letting the dogs back in I fire a few shots. That way I can shoot almost as often as I’d like, I’m not shooting for long but I’m shooting often.

    I’d like to see more of those simple wood and steel back to basics kind of rifles.


  6. Lots of good airgun information in this series of reports on the Diana 25.

    After slogging through the recent tests I imagine shooting this Diana 25 was like a day off for B.B. 🙂

    That 0.337″ group is impressive for a smooth bore. All the more impressive when you consider that the open sights on this older Diana 25 are crude in comparison to their later open sight designs. Nonetheless, lets see you shoot a group like that with those new fiber optic sights that are being slapped on so many airguns. Are airgun manufacturers listening?

    Guess a 6 lb trigger pull on a gun like this Diana 25 won’t starve accuracy if the second stage is crisp.

    I’m a fan of seating pellets flush and then seating them deep when I’m pellet testing a “new to me” low-medium powered springer. I’ve never seen significant differences in seating pellets flush vs. deep in pcp’s so I don’t do it anymore.

    This smoothbore certainly adds an interesting dimension to the “Rifling Twist Rate Affecting Accuracy” test that is ongoing.

    Be interesting to see what this fun little airgun package can do at 25 yards.


  7. BB;
    In some of the AR rifles, the small base die seems to give better accuracy due to the smaller re-sized case resting in the chamber the same way each time. So, it still may be worth a try. Also, I have had good luck with IMR-3031, 748 and H335 powders and Nosler Ballistic tip bullets. Even with your fast twist, you may also want to try 55 and 62 grain bullets.


  8. BB,
    I would wonder if head/skirt size isn’t the most critical factor in a smoothbore. The RS’s are 4.52mm? I know from reading about Smoothbore ML’ers that decent accuracy requires a very tight load. I notice that you are using all soft lead pellets — did you try hard lead pellets? I suspect they will not work as well, but can’t say for sure.

    Also, I have a theory about why the deep-seating helps. Somewhat counter-intuitively, it seems that it is more difficult to load tightly in a smoothbore than a rifle, since there is no space (i.e. the grooves) for the deformed lead to go into. By seating it, you are sizing each pellet so that less energy from the spring is expended on that step and minimizing variations.

    Anyway, 25 yards will be fun to see.

    • RE: “Sizing” via deep seating

      Since head sizes are smaller than skirt sizes, so there is some “sizing” when a pellet is seated, particularity in a smooth bore. But I don’t think that “sizing” is really the right idea.

      Springers have a violent pressure pulse which not only seals the pellet, but will distort the skirt. Once you distort the skirt then the consistency in shape from production is lost. I think the real benefit is that the extra space created by deep seating reduces the pressure pulse. Since there is extra volume and pressure is reduced, then the muzzle velocity of the pellet is also reduced.

      I think you could demonstrate this quite easily by shooting pellets directly into a 5 gallon bucket of water. (I’ve floated a thin sheet of foam packing material on the water so that I don’t get baptized by the splash.)


  9. BB,

    If the Dianna 25 delivers this level of accuracy at 10 meters, then does that mean that you will test other smoothbore, long air-guns (Daisy 840, Crosman 760, etc…) for us to see how they perform (preferably with more than 2-3 types of pellets…)?


      • BB,

        I’ll consider it. However right now the only smooth-bore airgun I have is a Daisy Red Ryder. I gave my Crosman 760 away to someone at my Church who will use it more than I did.

        One issue I see is that right now the weather is downright cold and I shoot outside at my parents farm. Since I have no desire to shoot when its 10 degrees outside, it would have to wait for warmer weather.

        The other issue I see is that I don’t have a chronograph so I wouldn’t be able to follow the 3 part test pattern you do.


  10. I have an Hill Pump MK3 ( ## WITHOUT the original hose) and getting a Walther Dominator

    which hose and adaptor do i need to buy ?

    Links from PA will be helpful


      • Thanks for the quick reply
        Actually i am buying it right now , the model is :
        Walther-2252013 [PY-1489-2668]

        i think i will need a hose and an adaptor , i have seen a dominator cylinder in our club and it does not fit directly with the Hill pump MK3 hose (also i didnt get the original hose wit my pump)

        So please suggest , i am standing by for your response as there are no live chat executive on PA site right now


        • Walther,

          This is Pyramyd Air’s blog. But we are physically located 1,200 miles from the Pyramyd Air warehouse, where this gun is (or will be when it comes back in stock).

          I don’t have the gun, so I don’t know the current fittings. You need to call the Pyramyd Air Tech Department and ask them this question. Specifications change all the time and only they can know what fittings are required.

          888-262-4867 — ask for the Tech Department.

          Had this not been an immediate request, I would have emailed them, anyway.

          By the way, this is a CO2 rifle that was converted to operate on air — not the original Walther Dominator made for field target.


  11. Thank you for the response

    And about the fact that this is a converted gun , i didn’t had any idea about that. Will be interesting to know about its history which you must have blogged down earlier . Will try to search it ; but would be helpful if you could point it out.

    Will mail the tech’s and wait for the response

    Thanks again

  12. BB,

    Just wondering here.

    Has the ammunition shortage that seems countrywide for powder-burning guns extended to include air gun ammunition? Is there a greatly increased demand for airguns that parallels the demand for firearms?

    Our Sports Club tried to buy a new Ruger 10/22 for a prize in our gun raffle, and found them to be non-existent locally.


    • Les,

      So far airgun ammo seems to be immune. I know what you mean about firearms ammo and reloading components, though. But some big companies like Midway USA are not using this time to boost their prices. I just bought 8 pounds of powder from them at a very reasonable price.

      I will remember that in the future.


  13. Hello B.B. and Fellow Airgunners. I thought I would weigh in with my thoughts and experiences in deep seating vs. flush seated pellets. I was looking at some pellet guns at one of our automotive-hardware-and everything in-between stores, and happened to get into a conversation with and older then me gentleman, who has been an airgunner for quite a no. of years. He proclaimed he had been shooting 10 meter air rifle for 30 years and was a proponent of seating pellets. To make a long story short, I find it works great in some of my guns, and not as good in others. As they are all equal in velocity,( under 500 fps). I have concluded that it has to be a number of factors coming to play. My 3 .22 cal. rifles do not like deep seating. Three of my five .177, seem to group better with deep seating. To me, this is as mysterious as why one gun loves JSB, and another Crosman. Any thoughts?
    Caio Titus

    • Titus…

      What is happening is that you are fooling with the pressure curve.
      It takes more force to start moving a pellet that is flush seated to the chamfer than it takes to move one that is pushed fully into the rifling. The flush seated snaps in and then progresses with less force required, while the deep seated only has the bore friction. This is ignoring inertial forces.
      So the pressure builds differently behind each and the piston has moved to a different position in the power stroke before the pellet finally moves. So where does that leave you as the pellet runs away from the pressure? Is it a point in the power stroke where the pellet gets the most out of the pressure curve or not ?

      I cobbled a test a while back to find out how much force it took to push a pellet fully into the bore.
      I think it was my .22 R9 with FTT pellets. Took between 5 and 6 lb of force to get the pellets to snap into the bore. I don’t know how many psi this equates to. Probably quite a bit.
      So how far has the piston moved and how fast is it going when you reach the break point (pellet starts moving) ? The piston is trying to make pressure while the pellet is moving away and trying to reduce pressure.

      In theory getting the most out of the power plant (best utilization of the power curve with max power out and tightest velocity spreads) should give you the best performance. But then there comes a little problem. A happy power plant does not necessarily guarantee accuracy. I have rifles that tell me this for sure.

      I am not going to proof read this. Probably my longest post.


      • Lets see… Possibly fallacious thought process

        PI * (0.22 / 2.0)^2 => 0.038 sq. in. (area of circle)

        1/0.038 sq. in. x/6 lb

        6 * 1/0.038 = x

        x = 158 PSI… Sounds a bit low for initial engagement…

      • Hello Twotalon. Thank you for your lengthy explanation. What you say makes a lot of sense, and gives me points to ponder. What I forgot to add in my comment, was my HW80 in .20 cal. has a very tight breach. If I didn’t seat the pellets deeply, they would be coming out of the barrel in the mid three hundreds. As you stated, it does make the piston work differently. The deep seated pellets are also a lot more audible then seating them flush. Not as bad as a dry fire, for sure. It is definitely noticeable though. Again, thanks for the reply. You have provided a new direction for me in my quest for understanding. To quote Hamlet. To seat or not to seat? That is the question.

        • Titus…

          Did you chrono that HW or are you guessing ? You would be surprised how often things don’t work the way you think they would.

          Let’s try some the “everybody knows” stuff with a SPRINGER….
          “Lighter pellets shoot faster than heavier pellets”.
          “Lighter pellets produce more energy than heavier pellets”.
          We are avoiding pneumatics here. This is about springers, so that last statement would be backwards for the pneumatics.
          By selecting the right two pellets to compare, I can either prove or disprove either statement with the same rifle. How about that ?? I just set up the conditions of the test to get what I want.


  14. Those Beeman Devastators lived up to their name–all over the target. A smoothbore may affect the range of the pellet disproportionately although given that pellets don’t rely that much on spin, perhaps not.

    Wulfraed, you’re right. No more tweaking of cartridges to create the perfect ammunition. Also, I’ve heard of Eric Bubi Hartmann, the highest scoring ace of all time. A quote from him is one of my favorites: “There is a big difference between playing at war and being at war.” Well, he certainly lived his creed. During his years of imprisonment in Russia after the war, he would clobber interrogators with chairs regardless of the consequences. Is that tough or what?!

    Such a shame, the gun debate is taking place just when fantastic new AKs are appearing. The fit of the parts is tighter although without diminishing the reliability, but they’re getting 2MOA with match grade barrels!

    But the gun debate is having much larger effects than I had anticipated. Part of background checks is instituting them for gun shows. It occurred to me that this might affect my quest for a Russian capture Mauser. These like other surplus rifles are dwindling. So, the only way to get them is through resale at gunshows. The guy I use regularly tours gunshows and vacuums up all the good rifles, so checks would really slow down his process and reduce availability. It looks like now is the time to make my move.

    Thus, unexpectedly, I have found myself thrown into the breach dealing with gunstores again. Things started out well. The guy I spoke to about their transfer policy was at least knowledgeable and confident although he rolled down the information too fast for me to get all the details. On the other hand, I see on the Internet that since I’ve dealt with them, this place has had a large explosion on its indoor range which the owners are not commenting on. And there was another Internet comment about someone getting killed on the gun range. It will be in and out quickly for me.

    But isn’t there a term for some phenomenon that deludes sailors at sea–like a mirage? I went back to one online dealer and found that the old crocodile who answers the phone has grown even more irascible. She couldn’t tell me some basic details about the gun I wanted and had to find the store manager–a big imposition that got her warmed up. When I told her that my gunstore wanted her to contact them for the FFL, she raged about the lack of trust in modern society. She took my credit card number as if she was doing me a big favor. There were also weird long pauses when I don’t know what she was doing. Then when I asked her the time frame for shipment, she squawked that she was so busy she didn’t know and maybe she would get to it next week. And with that, I was shrieked off the phone. Even with the checks I’ve done on the quality of this place and the good product that I received before, this is pushing it. I try to see my self-control as a victory of its own. And I also imagine that I am suffering the miseries of the Eastern Front just like the owner of the rifle that I’m getting from this person…


    • Matt. Your comments never fail to inform and entertain. Sometimes when I see a longish comment, I just skim over it and glean the interesting parts. With yours, I am able to read through with ease. I can imagine the alligator acting put out by your phone query’s. I can say for myself, I have been down that road a time or two myself. In a kind of weird way, it makes your day knowing these type of people are being put out.

    • Well, nothing has pasted yet. As for back universal ground checks, if they pass and say friend I have knowen for 30 years wants to buy a gun from me. Why I’ll run right over to someone with a FFL, pay him/her a fee, and make sure this guy is OK with the Feds. Yes, I’m sure this will happen.


    • Matt61,

      Re: Your concern that background checks at gunshows affecting your quest for a russian mauser

      I don’t know if your fear of background checks is rooted in a proposed State amendment or the Federal mandate but here in Colorado we have been required to have background checks at gunshows since 2000.

      Our State Constitutional Amendment language was debated for years before the ballot issue was passed by a 70% vote in 2000. I supported it.

      Our 22nd Amendment that requires background checks at gunshows basically follows the Federal Law as it applies to FFL’s (people in the business of buying and selling guns). Private individuals as well as curio’s, relics and antiques are exempt from background checks (out of State purchasers have the same restrictions at our gunshows as the Federal Regs require for long guns and pistols).

      CBI’s (Colorado Bureau of Investigation’s) database is used for our background checks. Cost is $10.00 (ten dollars. Limited by the law.) Buyer or seller can pay. It takes an average of 20 minutes but I’ve been at large gunshows that have crashed the CBI server or overwhelmed the weekend CBI staff where background checks have taken over an hour. Yes, it’s inconvenient when it happens. Yes, it’s frustrating when this happens but in the big picture it’s a small price to pay IMHO.

      Initially in the early years table sales at gunshows dropped. The reaction by some was I won’t comply, don’t need the aggravation, don’t need the additional delay, cost, etc. Within 2 years the table sales were back and since then the table sales at all of our well run gunshows have increased.

      I would suggest, with the caveat of the wording in the pending legislation that you are fearful of, that background checks by themselves won’t impede your search for a russian mauser.


      • Kevin,

        I will weigh in on this one. THEY (the feds) already do background check at guns shows — by law! All FFLs MUST do a background check before selling a firearm, or, if the buyer( in Texas) holds a Concealed Carry License, that replaces the mandatory check, because the CHL check is even more invasive.

        To have ANOTHER state-run check is redundant, plus it makes individuals not able to sell to one another. That I do not care for.

        All a law like that does is drive private sales underground, and when that happens, all bets are off.

        Keep the laws we have and please don’t give us any more.


        • Tom,

          I understand your point of view and in general agree. As I stated in my 3rd paragraph private individuals are exempt from background checks in Colorado. Very common at our gunshows that individuals walk around with guns slung over their shoulders with for sale signs on them. Although those transfers are exempt many buyers will pay for a background check to verify that the gun is not stolen.


            • Bingo.

              The CBI background check is primarily for the firearm. The fed check is for the buyer. They’re both done in Colorado through the CBI computer system concurrently. The costs in 2000 for additional manpower and computing systems, especially for weekend gunshows, was around $500,000 but came in at $350,000. The savings was primarily because of compatibility with existing computer systems but the weekend manpower cost was accurate. Don’t know what the costs have become since 2000 but it will take another amendment for the cost of our background checks to increase from $10.00.


  15. BB,You said the DIANA 25 was not chocked.The barrel is a smooth bore.Yet the targets in this test show nice round holes.So the pellets must be hitting straight on, and thus must be stable right out or the barrel,So,to answer my question of the last blog;pellets don’t need any particular distance to initially stabilize -no matter what the twist rate is.Did I get that right?-Tin Can Man-

    • The question about pellet stability isn’t easy to answer as you posed it. Let’s say that there are a first and second order effects.

      For the first order effect, a diabolo pellet (not a bullet) does not to be spun to fly in a stable configuration. In other words, a diabolo pellet won’t tumble end over end. Over distances longer than 10 meters spinning tends to reduce group size. BB’s experiments in twist rate are trying to examine interactions between spin-rate and stability (as measured by group size).

      The second order effect is smaller and due to disturbances of the pellet as it exits the muzzle. In general these disturbances are thought to decay as the projectile travels down range.

      The gist here is that ballistics has really complicated interactions between a number of factors.

      • Maybe we need another test with the smoothbore…

        Load the pellets tail-end-first.

        If they act like badminton birds they should flip over fairly close to the muzzle, and the group size probably won’t enlarge all that much (2X, perhaps)… Velocity will be down from blow-by.

        Might need to run a thick glob of putty in a “silent” trap at one foot intervals to determine pellet orientation at point of impact — that would illustrate where in the trajectory the flip has mostly completed (I visualize some wobble beyond the initial flip which may reduce downrange velocity).

        • Pardon the “talking to myself”

          With badly formed pellets, the smoothbore may be more accurate/precise.

          Consider a pellet with a very thing skirt on one side, and extra thick on the other. Out of the smoothbore the trajectory is basically affected by aerodynamic stability.

          Add in the effects of rifling and you now have a situation where the center of mass (as viewed from behind the pellet) is not aligned with the center of spin. Centrifugal forces will try to push the center of mass even more to the side. The extreme would be a pellet so unbalanced that it transitions to looking like a cheerleader’s baton being twirled.

          • Wulfread,That would be interesting if one could photograph each glob and view them.It would maybe look too choppy as a movie,but would look good as an extended sequence.Can you imagine the pellet swinging around too far from it’s momentum and then swinging back?I wonder how much it would oscillate before drag dampened the action out…cool idea.-Tin Can Man-

            • You’d probably need a very high-speed camera (which means very bright lighting — if you consider that a 600W photo lamp only produces 1/20s @ f4 and 5 foot distance, and you want a minimum of 1000 frames per second <G> )

              Is Mythbusters still in production? {Since my lay-off I’ve been limited to broadcast stations only [well, my apartment complex pre-wired cable isn’t blocking/scrambling broadcast — including TBS and WGN, and my TV has QAM tuner, so it can tune those even though I’m not paying for cable]} This might be something for them to evaluate (with both smoothbore and rifled barrels).

        • RE: Firing Pellets backwards

          BB has recommended this in the past for a pellet that mushrooms well. Only good for short range since the pellet has lower BC when tail first. Also the pellets evidently tend to flip over to the head-heavy first configuration. So pellets don’t flip end over end continuously, but once from qusi-stable tail first to more stable head first.

          • Hence my suggestion with the smoothbore… Spin stabilized will have two opposing forces — the “badminton bird” flip fighting with the gyroscopic effect of the spin.

      • Thank you Herb,it’s what you called “secondary effects” which I had read about with bullets that set me to wondering.I’ve been learning about the more complicated cause and effects in exterior ballistics and BB keeps priming the pump.-Tin Can Man-

    • TCM,

      That’s right, the barrel is not choked. And yes, at 10 meters the pellets are stabilized. The question I have is, will that continue to 25 yards? That’s why I want to shoot at least the JSB RS pellets at that distance. If they group well then we’ll know. But maybe I should throw in a wadcutter like a Hobby, just to see the shape of the holes?


      • BB,You are both taskmaster and slave here;far be it for me to add to your labors.I think it could lead to stronger evidences.At that greater range the grouping should certainly be more to individual hits.Won’t irregular holes show up well anyway?-Tin Can Man-

        • TCM,

          I think they will — yes. But I needed a second pellet to test and only the Superdomes were accurate enough to carry over with the RS, so adding some Hobbys shouldn’t tax me. I’m only going to shoot seated pellets this time — because now I know better.


  16. I just saw the Evanix Rainstorm 3D Bullpup Air rifle. That has to be the UGLIEST airgun I have ever seen. It doesn’t even look like a gun. it looks like an aluminum Lego to me. Anybody else seen this abomination yet?

      • Well to each his own taste. I prefer to have a gun that looks like a gun. I don’t like surprises like thinking I am picking up a construction girder and end up being shot by the thing when I try to use it for building something. The Airforce guns are as non-traditional as I plan on getting. If you want a bullpup one of the best things I have seen is a talon with one of those maddog custom stocks under it and a 12″barrel and end cap. They look totally dangerous.

      • Morning B.B…. Sidebar: You recall the conversation about dripping oil down the bore of my Diana 25. Well, I dripped 12 drops of 30W Non-Detergent down yesterday and it is standing upright on its butt. So, I’ll wait a week or more. Then, I’ll pull patches through the bore and then shoot it. Is that all there is to oiling the piston seal ? The front trigger guard screw arrived from T.W.Chambers ( Established 1823..What ! ) and breech seal. Do I just pop out the old breech seal and squeeze in the new one..?
        Thanks for the interesting Blogs and say “Hi” to Edith..

        • Pete,

          You can shoot your 25 right now. It only takes an hour or two for the oil to soak in.

          You don’t have to clean the barrel, either. But you do need to watch the first 20 shots or so, because oil droplets will be blown out the muzzle. After than, everything will be fine.


  17. Hi, I am new to co2 and am getting a crosman 357w in a few days. I don’t know very much about proper safety with co2 or how to use it. Any help or links to help is much appreciated.

    • Ryan,

      Here are some tips for any CO2 gun.

      First and foremost, ALWAYS put a drop of Crosman Pellgunoil on the tip of every cartridge you pierce. The oil will be blown through the interior of the gun’s valve and get on evert sealing surface, where it will keep the seals fresh for many years.

      Second, CO2 is a temperature-dependent gas. Pressure varies with the temperature. It doesn’t do very well below 60 degrees F or above 90 degrees F. If you lay your gun in the sun on an 80-degree day, it will build up so much pressure that it will fail to work after about 15-20 minutes. Just let it lie in a shady place for a half hour and you’ll be back in business.

      Third, as you shoot, the gas cools the gun. So the velocity drops, because the gas doesn’t achieve the pressure that’s needed. By waiting 10 second between shots and shooting where it is at least 70 degrees, you can offset this.

      Enjoy your new gun!


    • Hey Ryan …

      There was a day in the not too distant past that I was in the same situation you are. I found what I was looking for in the wonderful videos on Pyramid Air’s web site called “Airgun Academy”. I am not sure how many of them there are … maybe 30 or 35 … and they are great. They are very well done, short, right to the point, and they don’t waste your time. You can easily watch three or four in a row and still remember what you learned. They are a really great foundation for anyone coming into the sport. I urge you to check ’em out.


      • I did check out airgun accedemy video. It was helpful. I was going to go out and buy the pellgun oil today but realized I already have “gamo air gun oil” can I use this to seal off the co2? And can I use this in the compression chamber of my TR77?

        • Ryan,

          Gamo hasn’t been too consistent about the oil they sell. I have used a product by that name to seal CO2 cartridges, but I can’t recommend it for a spring piston gun, unless the gun is a low-velocity model that can use household oil on the seal.


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