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Ammo Big Bore airgun calibers

Big Bore airgun calibers

Tom Gaylord
Writing as B.B. Pelletier

This report covers:

  • The greater problem
  • The beginning
  • Bullets — not pellets
  • .308 caliber
  • Bore size
  • .357 caliber
  • Black powder
  • The .45 caliber dilemma
  • Shoot soft lead bullets that are slightly larger
  • Other big bore calibers
  • Summary

Most shooters are familiar with the smallbore airgun calibers of .177, .20, .22 and .25. Even shooters who don’t consider themselves to be airgunners know at least the .177 and .22 calibers. But in recent years there has been an explosion of big bore airgun calibers, and I am seeing that many shooters have little knowledge about them. If that were the only problem it would fix itself, because over time people always learn.

The greater problem

The bigger problem are the airgun manufacturers that do not know much, if anything, about the larger calibers. This report will address the lesser-known truths about big bore airgun calibers.

The beginning

Where do the big bore calibers start? Well, they start at anything above .25 caliber. But there is a big bore caliber called .257 that is a legitimate .25 caliber. The difference is the .257 big bore shoots elongated bullets rather than diabolo pellets. Instead of 45 grains they can weigh 100 grains and more. They can reach out hundreds of yards, where the wasp-waisted hollow-tailed diabolo falls off fast after just 100 yards.

Bullets — not pellets

Another thing is big bore airguns shoot bullets, for the most part — not pellets. Yes, there have been some .308, .357 and even .45-caliber diabolo pellets made for certain airguns, but big bore airguns have been around since about the year 1350 and they have always used bullets — round balls until around 1850 and conical lead bullets since then. The diabolo pellet is a 20th-century invention.

.308 caliber

Recently the .308-caliber big bore has gained a lot of traction in the marketplace. People hear the caliber size and envision the .308 Winchester cartridge that they know is very powerful. But a .308 caliber pellet driven by air is far less powerful. It gives up the one big advantage of the big bore airgun — size. With a .308 air rifle your shot has to be precise or you risk wounding your quarry. That said, the .308 can do the job for a good shooter.

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Bore size

Now let’s consider bore size for a moment. You don’t have to do that with a pellet. A .22-caliber pellet should work in most .22-caliber airguns. Accuracy will differ from pellet to pellet and we sometimes sort pellets by the diameter of their head, but that’s as far as it goes. Not so for big bore bullets! And this is where shooters new to the shooting sports get confused.

A .308 bullet may be very accurate in a .308 big bore airgun, or it may not even stabilize. That gun may need a bullet that’s .309-inches in diameter to work well. It all depends on the size of the bore! You see, smallbore airgun barrels are closely controlled to fit the pellets of their caliber. But big bore airguns can have barrels of widely varying internal sizes. That’s because there are no set standards for barrels of big bore airguns. They tend to be firearm barrels that have been used on airguns.

There are exceptions, of course. AirForce Airguns, for example, orders hundreds of barrels in each big bore caliber they produce from Lothar Walther. They are such a large customer that they can specify the exact inside dimensions, as well as the rifling twist rate. That’s something that Joe from Podunk, who makes 50 rifles a year, can’t do. He has to select his barrel from the stock items a barrelmaker offers.

.357 caliber

The next size up from .308 is .357 — and this caliber is a huge problem! Ten years ago it was called 9mm, which is sized 0.355-0.356-inches in diameter. The Koreans who were the first to make rifles in this caliber made them with barrels sized for 9mm lead bullets. The trouble with that is, unless you know where to look, it’s very hard to find 9mm lead bullets. That’s because 9mm is mostly a pistol caliber. All the bullets that are popular for 9mm pistols are jacketed and don’t do well in airguns — especially not the underpowered Korean ones! It took a full decade for the airgun makers to realize their mistake, and it took dealers and shooters even longer. Even today there are many shooters who think one-thousandth of an inch shouldn’t matter that much with a bullet. But it does!

Black powder

This is where a background with shooting black powder firearms comes in handy. There are two big reasons for this. First, when black powder explodes upon firing, the instant high pressure upsets the base of lead bullets, obturating (squashing) them into the bore. They are squashed into the rifling where they fit the bore better and also seal against the burning gasses. Airguns cannot do the same, so the fit of the bullet to the bore is critical from the start.

The second reason a black powder background or at least a knowledge of their history is important is because in the past (1250 A.D. to 1900) all non-military firearms (read that as black powder, because that’s all there was for most of that time) came with bullet molds when they were made. The owner had an idea of his gun’s caliber but it didn’t matter as long as he used the mold that came with it to cast his bullets. The military held gun makers to more exacting specifications so they could produce the bullets for their soldiers. Their guns didn’t have to each come with a mold.

Today, though, black powder arms are produced to more exact specifications, so their owners can purchase bullets to go with them. But it still isn’t a smooth road.

The .45 caliber dilemma

Now we come to one of the biggest dilemmas in big bore airguns today — the .45 caliber that exists in no less than three distinct sizes! And they are not interchangeable. Starting with the Koreans again, when they made .45 caliber big bores they made their barrels for bullets of a diameter of .452-inches. That is the modern .45 pistol diameter for the .45 ACP cartridge. And some .45 Colt revolvers also have bores that size. 

Bullets made in that size are expected to be fired from .45 caliber handguns at 850 f.p.s. or so. They weigh from 160 grains to 250 grains — AND THAT IS IT! If they are shot in big bore air rifles in the 200-225 foot-pound class, they are fine.  The Turks are also making their .45 big bores with bore diameters in this size. I have no idea of what the Chinese who make the big bores for Gamo are doing, but it does bear consideration.

The next popular size of .45-caliber bullet is .458, and it has another problem. Some makers are calling their rifles a .457, but I doubt you will find bullets of that size unless they are custom made. Don’t worry, though, because .458 bullets are what you want to use anyway. They fit the bore, where .457 bullets usually don’t.

These are the air rifles that shoot bullets weighing 350-500 grains. They will also shoot the lighter bullets, as long as they are sized .458 and not .452.

Then there are the big bore rifles that are made by boutique makers who turn out a few guns a year, in caliber .454. These guys don’t last that long and finding bullets for their rifles can be a real chore. This size was for Colt Single Action Army revolvers from decades ago. You’ll have to go to a custom bullet maker to buy them today.

So — they’re all .45 caliber, but in three different sizes! Did you know that? If you didn’t and you shoot your rifle with the wrong size bullet you aren’t going to do very well. A 24-inch group at 100 yards can shrink to a 3-inch group, just by using bullets of the right size!

Shoot soft lead bullets that are slightly larger

So—the lesson today is to shoot lead bullets of the right diameter. The right diameter is one-thousandth over the bore diameter in most instances. But you need to experiment with different sizes to make certain. I have been doing this for over 50 years and in my experience a thousandth larger with a lead bullet is what you want.

They should be soft lead bullets, because hard cast bullets will leave lead deposits in the bore. Air rifle bullets also don’t need to be lubricated — as long as they are soft lead. In fact they shouldn’t be. They are ideal for the velocities at which the most powerful of these air rifles shoot — generally 700-900 f.p.s.

Other big bore calibers

Yes there are big bores in calibers other than the ones mentioned here. A number of rifles in .40 caliber have been made, but they were all made by low-rate or custom makers who probably made them to work with a lead bullet that is commonly available. 

That being said, there can be big bores in other calibers, as well. I know of several big bores made to shoot the 12 gauge rifled slug that looks like a diabolo pellet. It’s called the Balle Blondeau.

Balle Blondeau
The Balle Blondeau is a 12-gauge slug that looks like a diabolo pellet. Some smoothbore big bores have been made to shoot it.

Like black powder arms, a big bore airgun can be made in any caliber. If you plan to buy one, make sure you can get the bullets for it first.


This has been a brief but fairly complete look at big bore projectiles. I have concentrated on the bullets rather than the few diabolo pellets that exist, because the bullets are where it’s at for big bores. Stay tuned.

162 thoughts on “Big Bore airgun calibers”

  1. We have to mention the .50 caliber, I believe. They are now standard options for big companies. Evanix even offers the Rex Pistol in this caliber! Speaking of which I realized that you have never tested the Rex platform. Maybe you could do it some day, it would be an interesting comparison against the AirForce platform.
    A great weekend for everyone.

  2. Hatsan PileDriver, .50 cal!
    There are so many other Turkish air gun brands that don’t make their way down here – quite a few of them have .50 cal models. What we have here is the commercial kinda ones. We don’t even get the entire product line of Hatsan and Kral. By the way, Kral means king in Turkish. Down are the links for the Hatsans and Krals for Turkish market:

  3. BB,
    Do you think Hatsan 135 Carnivore and MOD 130S could also be added in the big bore list due to the fact that they are the only .30 cal piston rifles offered on PA?

    • Fish,

      I’m in the middle of a test of the Texan right now, but I see that the Piledriver is another powerful air rifle. I just got a load of bullets from Mr. Hollowpoint to test in the .45 Texan, so we should be seeing more big bore tests soon.


  4. BB,

    After reading your recent blog on the Dan Wesson 1911, and then seeing you talk about variations in 45 caliber bullets, it got me to thinking about a character in “Tarzan at the Earth’s Core” who takes down a stegosaurus with a 45 caliber pistol. For some reason I was remembering it as a 1911, but when I looked back, it turned out to be a pair of 45 caliber Colt revolvers. And the stegosaurus could fly– I always love what Edgar Rice Burroughs does with dinosaurs. Anyway, I guess that would justify using a big bore air rifle in one of the .45 caliber variations to take out a stego in the next big budget dino flick.

    I had meant when you posted your part 1 in the sharpshooter pistol resurrection series to send you a link to something dating from 1898 that uses a similar launcher or carrier structure for a small roundshot, but I had trouble registering an account at the time. US Patent 632838A to Augustus G Jacobs discloses a blowgun that uses the shot-centering launcher. Jacobs remarks that “by a device of this kind very accurate shooting can be done at moderate ranges with a blow-gun using shot as projectiles”, which tallies well with what you said about the accuracy of the sharpshooter platform.


    https://patents.google.com/patent/US632838A (an image of the patent drawings can be viewed here)

      • Now that is interesting! I did a quick search and saw your post on the AirForce Escape where you talked about him…ERB took science fiction in so many creative directions, so it seems appropriate that his grandson would be involved in advancing the science of airgunning. Now I’m imagining a green martian wielding an air rifle with a very long barrel that runs on high pressure helium…

  5. Fish,

    I replied back on another day with a suggestion about target darts. When I was growing up, it was easy to get ahold of EMT conduit, because my dad was an electrician, so I used that primarily for my blowguns back then. It did tend to rust a bit, but would stay usable for years and I still like EMT barrels. The blowgun I used in my spaghetti launching blowgun video is made with PVC. I’ve also used different types of aluminum tubes for barrels, and arrow shafts for small caliber blowguns. For darts I started out using finishing nails or dowel rods with paper or contact plastic cones, which still work well. The fastest dart I know how to make is the one using spaghetti with a special stabilizer. If you haven’t tried it before, instructions for a fast-to-make dart using only paper and tape are shown at http://tomshiro.org/pdart/ . Lots of other dart designs I like making, but won’t get into all of them now. Do you make any DIY darts?

    • MOS,
      This is crazy, man; I was about to ask you about that! 🙂
      I watched your video. How did you find a perfectly straight PVC? Impressive.
      My darts were very childish, made of paper, glue, and nails.
      I’ve decided to buy a 3 ft single piece .40 cal aluminum blowgun from Bass Pro. Whenever I can make time, I’ll also build the 4 and 2 ft PVC ones. IF I can make more time, I’ll give the 4 ft one wooden look and learn to make some authentic darts. For now, I am putting weight on the 4 ft pipe to straighten it out.

      • Fish,

        I used furniture grade PVC that I got at either Home Depot or Lowes, I forget which. It cost more than the run of the mill PVC but not that much, and had the choice of black and a few more colors. That’s a cool idea on giving the PVC barrel a wooden look. One of the things I like about blowguns is that even a simple-looking dart can be pretty accurate.

        • MOS,
          I thought about furniture grade PVC for the purpose. Is it more rigid and straight? Does it come flawlessly straight? Will 4 – 5 ft blowgun stay unbended when shooting or etc…?
          U can order 1/2 5 ft (2 pack) for 8 bucks. I can cut one 4 ft and two 2.5 ft ones. would u recommend furniture grade over the regular?

          • Fish,

            Is a little bit of bend THAT critical? I would not think so. Your aim (sight picture) would be the same,.. just adjusted for any droop.


            I did see some footage of some Amazon type tribe that was shooting monkeys with blow guns. The blow guns were REALLY long,…. like 8-10′ long.

              • Fish,

                Is bamboo straight through the bore (ID)? Is it tapered? The only run in with cane I have had is cane poles (bamboo) used for fishing as a young kid. It is tapered on the OD. It does have those joints/ridges every foot or so.


              • Fish,
                IIRC, a little bend is not going to affect anything since you are basically shooting instinctively. Your brain will automatically compensate to allow you to hit where you are looking.
                from Algona

  6. BB,

    I have the HM1000X in .357. From what I understand, it is actually .356 with a 1:26 twist. This air rifle was designed to shoot the JSB .35 pellet, which it does quite well. I have tried a few bullets in it, but because of the slow twist rate, they shoot a pattern instead of a group.

    In very recent years a couple of manufacturers have come out with bullets in this caliber that are lighter and shorter than the JSB pellet. Do you think these may produce better results?

    I have also been thinking of getting one of these for my air rifle.



        • RidgeRunner,

          I think round ball works in any typical twist as long as you can put up with the arcing trajectory. My experience is that fit to Bore is absolutely the driver for ball accuracy. Too small and it never ever gains the same spin and too big and it comes out looking almost like a (Rugby) ball with deep grooves. The DAQ .575 .(58 Caliber) Short Rifle 20″ barrel (hgh 600 FPS) and the DAQ .575 Pistol 14″ barrel (low 500 FPS) have helped me understand how each extra FPS effects the Internal Balistics of the .283 grain ball and especially the .350 grain hollow points. I think you need to see if hollow point are available to your specification and then get different overall lengths cast to find the sweet spot. If you can adjust Input pressure (fill pressure) and/or your valve output then find the combination that gives you the best accuracy. I’m still working on the two .575 and keep getting surprised by how much little changes make to the downrange results.


            • RidgeRunner,

              My experience with shooting the .575 round ball has been full of surprise. I started with the black powder info as a starting point but am not positive it is a direct comparison. The way you can alter the volume and flow of the aircharge in a Big Bore is just fundamentally different than a powder charge.

              I have used their product in my .308 as well as the .458. in the .308 i have been slowly increasing the length of the bullets to see just how long and heavy i can go with the 1:10 twist. They seem to be very good at consistent product; i hope they stay that way!


              • Shootski,

                A 1:10 twist is a good twist for long bullets. You will likely find that you can use any of the bullets if you adjust your power for such. You will also likely find one or two that are real sweet.

                • RidgeRunner,

                  That’s my thought too! The DAQ flows lots of air and really doesn’t slow down much with a well fitted (to the Bore) bullet. I have been ordering bullets from NSA and other sources starting with some 108, 111, 120 grain and plan on building my supplies of .308 all the way up as high as the 198 gn from: https://hunters-supply.com/ammo/pelletsbullet-c-27.html?osCsid=1ov70d695h1o4gfnir4maegpf6&osCsid=1ov70d695h1o4gfnir4maegpf6

                  eventually i will have launched enough of the lighter (cheaper) bullets that the DAQ is fully broken in; I’m at about 280 and it should be in the next two 100cf of air that i can get serious about getting serious finding the perfect round Form Factor. Once i have that ill buy a bullet mold or three in steel, brass and iron…maybe ill break down and buy one or two in Aluminium and see if it works for me. As Rk said, “It’s only time and money.”


            • RR, you are correct. I owned/shot a T/C Pennsylvania Hunter back in the day. It was a round ball BP rifle. It had a 1:66 twist. It shot very well compared to the faster twists (1:48 was a comprise if I remember right).


    • It’s only time and money. I’d first try the lighter, shorter bullets in the 1:26 barrel . If you could find them, a round ball might do okay. Then, after extensive testing I’d get the new barrel and start all over. Like I say, it’s only time and money.

      • Rk,

        I intend to try some of the lighter bullets in it. Some of them I have seen are as short or shorter than the pellet. They may do pretty good.

        As for a new barrel, a LW barrel is not that expensive and I have access to several lathes. The hardest part will be making it quiet enough that you do not need ear plugs, but that will not be hard either.

    • RR,

      Have you thought about getting some resizing dies (they seem to be reasonably priced) so you can dial in the exact size you need or is the twist also a concern?


      • Hank,

        The twist rate has a lot to do with it. Bullets like a fast twist rate, say 1:16 or faster. As a general rule, the longer the bullet, the faster the twist rate it likes.

    • RR
      I was hopping you would mention about your RAW and the .35 caliber JSB pellets.

      I still think the .35 caliber (pellet) is a good choice in some .35 caliber air guns.

      But that is what I don’t like about the big bore air guns. They use bullet sizes mostly and not pellet sizes.

      Big bore bullet shooting airguns are cool. But I still prefer a pellet shooting big bore air gun.

      If I’m going to shoot a bullet I prefer that it is a firearm that I’m shooting the bullet out of. Not a air gun.

      It’s just a me thing. What can I say.

      • GF1,

        The .35 pellet is actually larger than that. The bore on this rifle is actually .356. I have seen pellets for the .45 air rifles.

        If I can find a bullet that will work in this air rifle, I will be tickled. It does have to be pretty awesome though as this will shoot the 81 grain pellets right nice. I have put five shots in one inch CTC at 100 yards. We shall see.

          • GF1,

            Not too much with this barrel. I know that any bullet that will work well is going to be pretty short and therefore light. I have communicated with the dude who built this air rifle and he can make another barrel and/or up the power level if I desire.

            It really would not be that hard as the regulator is adjustable and the barrel is easily removable.

            • RR
              Do you think it would be worth it to spend the extra time and money to do the conversion to make it shoot bullets compared to the results your getting right now with pellets?

              One inch and under at 100 yards with a .35 caliber pellet is good enough for me. I would be a happy camper.

              • GF1,

                This is true. I really need to spend a lot of range time with this air rifle. As of right now, this air rifle is tuned to these 81 grain JSB pellets. The issue with the pellets becomes trajectory and velocity. By one hundred yards these pellets have slowed down so much that the power has dropped by almost one half. The trajectory looks like a rainbow with a drop of about three feet from a fifty yard zero.

                One of the things I wish to do is adjust the regulator upward in small increments to see how fast I can push these pellets and still maintain under 2 MOA at 100 yards, though my preference is 1 MOA.

                It would also be nice to have a hunting rifle barrel for this. In the state of Virginia it is legal to hunt deer with a .35 or larger air rifle. At fifty yards, I would have no qualms about shooting a deer in the head with this air rifle right now, but when you stretch it out to 100 yards I become concerned with the power drop. I would like my projectile to be carrying around 100 FPE at that range rather than at the muzzle.

                Will the pellet remain stable at that power level? I do not know. Probably not. To have that much power at 100 yards it would have to be moving pretty fast. That is why I have to give consideration to a different projectile which will require a different twist rate.

                I think I am entering another phase in airgunning. I am wanting to experiment with what is possible. That is why I would like to have a Maximus in .22. This basic platform is almost unlimited with what you can do with it, at least with small bore.

                I have “spoke” with the dude who owned RAW and designed and built the HM1000X. He has one that develops over 200 FPE at the muzzle. The “normal” regulated models can be tuned to 160 FPE. Now, we are talking.

                By the way, he is still in business.



                • RR
                  Maybe you should just stick to a firearm for those 100 yard shots at a deer.

                  I would want more energy than just border line energy.

                  If your getting down to 100 fpe of energy you better darn well make a good shot placement.

                  Not saying 100 fpe isn’t enough. But it doesnt compare to what a center fire can do. And I know you know what I mean.

                  • GF1,

                    Yes I do know. As for shot placement, that is paramount. Head shot. Period. I cannot gut shoot an animal.

                    I quit hunting in ’85 because I did not need to hunt for food anymore. If my family is hungry, I will hunt again. Hunting is not a sport to me.

                    • RR
                      So then why go to the bullet and barrel and tuning for the RAW if you stopped hunting in 85?

                      Sounds like a waste of money and time to me.

  7. B.B.
    If PCP’s are the Dark Side then big bores are the Black Hole! It sounds like all bullets/ammo/pellets should be expressed in metric. It is more accurate!

    In the first paragraph you said, “because over time people always learn.” I beg to differ. People never learn, that is what history tells us, sad but true…


      • Siraniko-

        The correct ending to that saying is:

        …….. are doomed to have wet paint on their hands!

        People can read the signs. All pertinent info is contained on the signs. People will still touch the wet paint. People are just people.

        • Amen to that.

          Although I think that people eventually DO learn. They only need more time.
          About a thousand years. Perhaps then they will stop looking for witch healers 🙂

    • Yogi,

      It is not more accurate, just different. I work with both every day. It is actually easier for me to use the standard measurements than the metric as I am on old geezer and that is the way I was taught. I do not think metric. I look at a nut or bolt and I think 1/2″ or 9/16″, not 10mm or 12mm. Fortunately, I know the formulas on how to convert to metric for work.

          • The SAE system is based on the old Dutch system of 1/8th fractions. What is the decimal equivalent of 3/32? Even stock trading has given up on the 1/8 increment system.
            When you redo your kitchen, using metric makes most of the hassles disappear.


            • Yogi
              First off remember I’m a machinist for to long for me to remember. Well was actually 36 years this last June.

              I work with inches and decimals and meteic and fractions all day long. And thats easy. What is half of 1/16 of a inch.

              To start with 1/16 of a inch is .0625″. So what’s half of that? Its 0.03125″. Why is that hard to do.

              And probably so in that trade.

              We hold half thousandth tolerance in my trade. Not a 1/8th inch. A 1/8th inch is like a mile to us in the machine shop world.

              See you only know what you know. There is whole nother world out there that walks a finer line that what your talking about.

                • Yogi and Gunfun1,
                  for easy to memorize fraction-decimal equivalents I like ninths and elevenths.
                  1/9 = .11111…
                  2/9 = .2222…

                  1/11 = .090909…
                  2/11= .181818…
                  3/11 = .272727…

                  Speaking of 1/8ths, when I was in high school, one of the cheerleaders’ cheers went like “2 bits, 4 bits, 6 bits, a dollar, all for the [insert team name here], stand up and holler!”

                    • Yogi
                      That’s similar to what I was going to say to your reply to me above.

                      19 over 128 is unrealiatic. Who would ever use that number besides you. 😉

                    • Yogi here this comment.
                      “You were the one who said, convert it to decimals and then use thousands. I’m just trying to get started…..

                      If you start with decimals you do not have to convert it to decimals.doh…

                      OK lets get fancy as a machinist, please remove.003″ from the 9/128 bar stock.

                      It’s going to Venus so it better be right! NASA contracts are on the line.


                      We would never get bar stock that measures that way.

                      Try again. I see you have never worked in the machine shop world.

                    • You were the one who said, convert it to decimals and then use thousands. I’m just trying to get started…..

                      If you start with decimals you do not have to convert it to decimals.doh…

                      OK lets get fancy as a machinist, please remove.003″ from the 9/128 bar stock.
                      It’s going to Venus so it better be right! NASA contracts are on the line.


              • GF1,
                Yup, we that are, or came, from a manufacturing background think differently regarding dimensions than others. Carpenters think differently than we do. That is the reason it is difficult for a machinist to be a good carpenter. We are always trying to measure things down to the .001″ instead of 1/16″. I am good at finish carpentry because I am meticulous and take a lot of time measuring and cutting. Sometimes perfectionism can be a curse…I have it!
                Going from inches to millimeters is like learning a new language. We will never think in the that language. It will always be a conversion we do in our heads. Lets see, a millimeter equals .039″ so 10 millimeter would be .390″, etc. If we learned the metric system from birth it would be easier for us. Now it’s worse than ever because the two systems are mixed together. How frustrating is it to work on your car and find that some of the bolts are 1/2″ and some are 10mm? Now we have to have both SAE and Metric wrenches and sockets to work on almost anything! Here in the US we will never go completely to the metric system because the cost would be enormous. It’s just crazy these days.
                Now lets see, my airgun is 5.5mm, oh that’s .040″x5.5=.22″…it’s a .22!

                • Geo
                  We have been using mm since probably 2000. Maybe even earlier.

                  But it’s simple to convert. If I need to make a move with my indicator that reads in thousands to equal mm I go by this.

                  .025 mm’s =.001″

                  So if I need to make a .100 mm move that is .004″

                  .075 mm=.003″

                  .05 mm=.002″

                  If I need to make a whole 1 mm move that =.040″

                  And notice I’m rounding up my thousands. It’s like a tenth over the actual reading which will mean nothing in most instances with the tolerance of the part.

    • Yogi,

      Thanks for this opening!

      I have ben reading the blog for a number of years and am always amazed at the range of understanding each of us brings with us and how we read and react to the Blog! As a Public Service i found this: https://www.mathsisfun.com/accuracy-precision.html

      I’m providing that link with tongun-in-cheekrest and also as a hook to get readers to go to the full site and see if even the best of us at Maths don’t have a few concepts outright wrong or maybe finally learn a thing that we didn’t get from a crappy Math instructor along the way.


      Choose (all of you) to enjoy or not!


  8. I’m a fan of the 40 cal. Well .410 really. I know, I know. The ugly stepchild. (Kind of like the 5mm/.20 cal.) Grain weights start at 170 and run up to 265 at least. I don’t know of anyone that makes the 170 gr.in lead. But I think if a 215-225 gr. bullet could be pushed to around 825-850, it’d be a killer.

  9. Your advice on having a soft lead pellet/bullet 0.001″ over, is right on. My “Long Nine” is quite fussy on this, and I have to size everything down to about 0.354″ to get things to work well.

    • DougWall,

      “bullet 0.001″ over, is right on.”
      Is that to the land or Groove? Just for fun.
      I use the Groove diameter and take it one step more; as the caliber of the projectile increases or decreases I use the area percentage growth to decide if i need to grow or shrink the oversize proportionally.


      • That’s groove. My barrel seems a little tight, and has a land diameter of about 0.350. If I try to chamber a 0.357, it just plain wouldn’t happen without a hammer.

        • DougWall,

          Wow! Keep the hammers in the tool chest!

          Have you slugged your barrel to determine the actual Bore Diameter? If not you really need to do that or have someone do it for you. Best to do it yourself since you learn so much about the entire length of the Bore while doing it.

          If the actual Bore Diameter is .350 then i would never go bigger than .3515 oversize. And that is measuring with a bullet Micrometer and not just Calipers. Calipers are just fine for measuring groups but just aren’t accurate at measuring Lead bullet Diameters. If you haven’t worked with Micrometers get a Machinist (the older the better) to teach you how to measure correctly.

          If Im preaching to the choir then don’t take it personally there are lots of folks reading this Blog that haven’t joined the choir yet…


          • Shootski,
            The 0.350 was just a quick measurement with a caliper. I have slugged the barrel, and my best measurement with a micrometer is about 0.3535. When I made my sizing die, I started small, and gradually opened it up until I got what seemed to be a good fit, with reasonable effort when chambering the pellet (not too easy). This size seemed to be right around 0.354.

  10. BB,

    You specifically mentioned that lubes should not be used with the pure lead bullets in big bores, and I was curious as to why that is. I would think it would help with leading issues. Wouldn’t a light oil or wax potentially help?

    Which leads to a question on chokes – are these used in big bore barrels? I would think not, especially if we are not lubing the bullets, but was curious. I don’t have a big bore as I don’t really have a use for one and can’t really shoot one at home, but I am curious.

    • Alan,

      You can get .30 and .35 barrels that are choked, but these barrels should only be used with pellets. The bullets just do not have enough give in them for a choke.

      Now I have seen bullets that were designed to work in a choked air rifle. They had several thin, raised rings along their length that allowed for some compression.

    • AlanMcD,

      I second BBs dirty the Bore and add that leading has not been an issue in my barrels and I think the basic reason is the low frictional heating, no repeat heating of powder charge burn, and absence of heat from a powder charge flamefront vaporizing the base of the bullet; part of the reason no one uses Gaschecks on airguns.

      I have not heard of anyone claiming to use a choked Big Bore barrel intentionally.


  11. BB

    Love all the history! So much to learn.

    Wondering how long it will be before some custom maker introduces a hexagonal bore air rifle with matching hexagonal lead bullets. Getting the twist rate right could be trial and error and expensive. But long range accuracy potential could make it worthwhile. The old English Whitworth made famous in our civil war had legendary accuracy even by most standards today.


  12. Interesting stuff B.B.!

    Question about terminology…

    In the past powder burner bullets have been used in airguns so the term “bullet” makes sense to identify them.

    More recently lead projectiles are being designed and manufactured specifically for airguns and are referred to as “slugs”.

    I have been asked a couple of times what is the difference and if slugs are for airguns, then what about 12 gauge projectiles that are called slugs? …All as clear as mud.

    So, should we refer to (non-diabolo, unjacketed) lead projectiles suitable for airguns as “slugs” or are we just going to suffer any confusion and use the terms “bullet” and “slug” interchangeably?

    Maybe the dividing line between big bore and small bore is enough to keep term clear – big bores use bullets, small bores use slugs. Or maybe by manufacturer – H&N and JSB are calling them slugs.

    Anyway, I’m easy. Just curious if there is any concensus on the naming convention.

    Happy Friday all!

    • Hank,

      A skunk by any other name still stinks.

      Why are they calling them slugs? Who knows. The only thing I can think of is “Well, it’s made out of lead, so it must be a slug. Da huh, da huh.”

      Just think. After all these years people have been shooting cast and swaged “slugs” in their firearms instead of bullets. Da huh da huh.

      P.S. The real sad part about all of this is it is probably the truth.

      • RR,

        Guess that it is a connotation thing…

        Say “bullet” and I think of a jacketed plastic-tipped 150 grain 30-06 round.

        “Slug” brings up an image of a Foster or Brenneke shotgun slug.

        “Diabolo” a pellet.

        …Maybe we should just go with Shootski’s suggestion and call them all kugels 🙂

        Have a great weekend!



        Oh, by the way. Skunks don’t always stink – they can but don’t have to LOL!

        We have a local family of skunks (mamma and 4 little ones) that I often encounter when putting out the garbage. They all act like cats – they love to be stroked and have their neck scratched. Currently, they are helping me get rid of those white grubs in the lawn …I pay them with a couple of pieces of Honeycomb cereal (guess that is desert for them).


          • Chris,

            Sorry – that is NOT going to happen!

            Triggering a flash with 5 skunks within touching distance is the best way to get sprayed that I can think of. They are all very calm around me – like to keep it that way 🙂

            • Hank,

              I did not think of that and the fact that they are nocturnal,.. for the most part. Oh well,… that is pretty cool that you can do that though.


              Still?,… there ought to be a way………….. 😉

              • Chris,

                I have seen skunks out as it is just getting dark but it is usually full dark before they think about foraging. I usually see my stripped family 10 – 10:30 in the evening.

                They are fun to watch. Before all the young ones got over their shyness I would give the bold one a Honeycomb and he would run off with the other three chasing after him – halarious because they kinda waddle when they run. Now they all crowd around pushing and shoving wanting to be first for a treat. I only give them 2 Honeycombs each so not to spoil them.

                Lots of critters around here.


                    • Shootski,

                      I unfortunately have had to try that in the past and it does not work so well. A better “solution” is 1 part baking soda, 1 part peroxide and 1 part dish washing liquid. It works.

                      I have also heard of applying baking soda before bathing with the above solution to absorb the oil before it is rubbed into the fur.

                      There are also some solutions you can buy that work pretty good. It is a good idea to keep some on hand.

                  • GF1

                    As I said to Chris, I wouldn’t want to try a camera flash. Something like that would startle them pretty bad and blinding them with the bright light would make them very nervous – not good!

                    The skunks are pretty laid-back creatures – with their defense mechanism no wonder that they are confident eh?

                    I found that sitting down (so not to loom over them), looking away from them (looking directly at an animal is confrontational and threatening), keeping movements slow and talking in a soft voice lets them relax. Like most animals, skunks are curious and given time come to trust you.

                    They are fun to watch.


                    • Hank
                      True. But not for me.

                      If you get sprayed you for sure will have some social distancing for a few weeks.

  13. Nice article Sir.
    Bigbores seem to be gaining more interest mainly because more powerful models being offered, and more mass produced softcast/swaged boolits from more makers. There’s also the rabbit hole of handcasting for bigbore airguns, I fell in head 1st. Main reason I cast my own is for cost savings.
    Sizing is everything in any type of airgun, but bigbores seem to be even more finicky. I use a push thru sizing die for most of my handcast boolits.
    Let’s not forget about .375, and .575, I have one of each from Mr. Quackenbush. The .375 XL I own, the barrel was made to use Hornady box roundballs, the .575 barrel was crafted to shoot handcast roundballs as dropped from a Lee mold.
    Not only are there new options for bigbore airguns, there are a few people converting to even smaller .172 caliber. The .172 offers high BC, high sectional density, and they’re cheap to cast 🙂
    Hope to see you at an airgun show next year BB, 2020 has been rough.

    • Erockrocket,

      Those are beauties. I haven’t been casting boolets since the old days but those look good.

      Do you coat the inside of the mold with beeswax? There is probably some new synthetics for that now.


      • Benji-Don,

        I learned casting from reading a book: From Ingot to Target: a Cast Bullet Guide for Handgunners. And then spending hours and hours on getting bullets cast well enough to be shootable. I learned that the mold and especially the mold cavity and sprue plate needed to be operating room clean using automotive cleaners and finally Everclear to wash the molds. Never used anything to coat a mold…am I TOO Old School on this?


        PS: the book is available Online: http://www.lasc.us/Fryxell_Book_Contents.htm

        Worth a look if you have some time or for other readers interested in going down the casting path… Cliff

        • Shootski,

          I think the old timers did not have automotive cleaners and would not waste the everclear on a bullet mold. It was a long time ago for me. The beeswax seemed to work real well. I think the soot from a candle flame also helped. I was taught by an old time black powder shooter. My rememberer is not good. I know my bullets came out near perfect once I got everything running right. Then it was time to keep casting.

          I still have lead and molds but I have not used them for a long time. Just curious. I liked the older steel molds better than the aluminum ones.


          • Benji-Don,

            Yes on the Steel over Aluminum (since i never used any) but also have some old brass ones.

            Yes on getting some carbon into the cavity always just use a stick carved/notched with a knife blade like a fire stick.


  14. BB,
    Thanks for the short course on pellets/bullets. I think that I have read or heard all of it before, but not all in one place.
    You were talking a while ago about muzzle loading airguns being a bad idea, but what about the old schutzen rifles that were muzzle/breech loaded? A ‘false muzzle’ would be placed on the end of the barrel to load the bullet from the front, all the way down to the chamber (fully engraved rifling to bullet engagement) and the breech would be loaded with a primed brass case, filled with a powder charge (with a card ‘wad’ over the powder). Very accurate system.
    Do you suppose that there might be an increase in accuracy, seeing that the base of the bullet (slug) would have minimum deformation? Maybe you could get a false muzzle made for a Texan?
    Just wondering.

  15. Got the notification that the semi auto Marauders are in stock now.

    They only show it in .22 caliber right now though.

    The 3 reviews on the PA website are pretty positive. One talks of jamming and the other two say no jamming at all but all say are accurate and fast. And only one mag comes with it which is a bummer and no extras are available yet. And the semi auto mags are suppose to be different than the regular Marauders. So a no go there on using regular Marauder mags.

    I think I’m going to wait and see what happens when more reviews start popping up. Plus I would rather have one in .177 caliber. But definitely interested in one. I almost pulled the trigger and got one. But I think I’m wating to see what happens.

  16. Ok
    Everybody keeps talking bullets and big bores and twist rate for the bullet and conversions and all that other hipe.

    Well how about lets talk what kind of groups are you all getting with your bullet shooting air guns. And how much are the bullets compared to pellets?

    And lets scratch cost of pellets or bullets. Lets talk accuracy and distance.

    Who will be the one that shows me evidence and can tell me why I should go bigbore and convert to bullet shooting air guns.

    Right now I got room to shoot and I have shooting ranges by the house. And a reminder. I can be happy target shooting a big bore air gun bullet shooter. But it better darn well be accurate.

    I want to see some targets.

    • GF1,

      I think there is more than enough stuff out there with some people getting some pretty awesome results. Problem is,… it is scattered all over the web. Unless you stay up on the matter,… it is a bit hard to stay up on the topic,… or even catch up.

      If you are waiting for someone here to magically pop out pics of 1/2″,… .45 cal. groups at 100 yards,… I think you will be waiting awhile.


      • Chris
        Well what better than this one place here.

        Maybe BB will continue with that in future reports.

        But as I see it we already had enough discussions about what if.

        How about some more accuraccy results from different airguns with bullets.

        I know he said he just got some Edgun bullets for the Texan. But what about all these other bullet shooting air guns.

        From reading the comments today I would say that others here have already experienced what air guns and bullets are working. Don’t you get that out of the comments.

        Shootski is pretty adamant about big bore air guns. He should have some targets I would hope that he could show and help with the discussion.

        Thinking more maybe is should be reading the other blogs and forums out there.

        My thought is why is this such a mystery. Someone has sure have to have some accuracy results.

        • Gunfun1,

          I don’t take lots of pictures of my targets unless they are teaching me something.
          The image is of the DAQ .308, 1:10 at 50 meters, 3,100 PSI fill, 72°F, NSA 138 gn. It was the first 5 shot group and what it taught me was that as usual the POI climbs and the 5th shot is going to be effected by the tube moving the POI. It means the DAQ .308 at this beginning fill pressure with this bullet is good for 4 shots and one Coupe de Grace at close range. This was shot Off Hand at 10 power Trenier 4×16×40 SFME.

          What I learned from this Target:

          If I want to call it a 1 MOA shooter I need to limit myself to 3 shots max or remember to hold for the tube induced movement on shots 4 and 5

          As I told RidgeRunner above a ways I’m still working on this rifle looking for how heavy of a bullet it can stabilize.


          Edit: should have rotated the pivture…duh!

            • Gunfun1,

              Thank you! I shoot Off Hand because i use Big Bores to hunt. I don’t Still hunt, or Treestand, or hunt from a Blind; I Stalk CLOSER. I used to hunt with PB and it got boring and didn’t feel like Fair Chase when I could pick off Deer or Elk at over 500 meters…i don’t like spearing fish in a barrel either! So that’s why I shoot Big Bore Air.

              It was late when i posted the DAQ .308 group and i didn’t want to take the time to answer some of your questions about why shoot bullets out of airguns just then.

              “Well how about lets talk what kind of groups are you all getting with your bullet shooting air guns. And how much are the bullets compared to pellets? Commercial Big Bore Bullets are more expensive because they have more Lead. You could cast/swage your own and it lowers the price dramatically if you turn out enough bullets to amortize the cost of the casting/Swagging gear. I have no clue if Commercially produced small bore bullets that weigh the same as a pellet should be more expensive.

              And lets scratch cost of pellets or bullets. Lets talk accuracy and distance.

              “Who will be the one that shows me evidence and can tell me why I should go bigbore and convert to bullet shooting air guns.” My opinion…only if you hunt/pest big enough prey.

              “Right now I got room to shoot and I have shooting ranges by the house. And a reminder. I can be happy target shooting a big bore air gun bullet shooter. But it better darn well be accurate.

              I want to see some targets.”

              I showed you one target that shows the precision of my DAQ .308 on paper with that bullet I think you know that it is a simple matter to dial the scope so that three shot group is made not only precise but also accurate. But that isn’t why i was shooting that day. I’m looking for a hunting/pesting bullet. I want to put down 250FPE (339Nm/339 Joules) out to 100 meters. This bullet only gets me: 100 meters, 244MPS, 266Nm (266 Joule/196FPE) -280mm DROP, 0.0 (NO WIND DRIFT) 0.348TOF So i need to get some heavier bullets or go a lot faster because i want to stay sub transonic that doesn’t get me much. Out to 75 meters the trajectory is almost flat; from -38 to maximum of +23mm and then -53.5mm at 75meters which is really nice for hunting.


              • Shootski
                Sounds like alot more work than shooting pellet air guns verses bullet shooting airguns.

                And yes accuracy is important. But no way around it cost is reality too.

                I’m one for modding and such but just seems like alot of work to me to shoot bullets instead of pellets.

  17. Off topic, still fairly new to airgunning and need some repairs done. Does anyone know of someone in Missouri or even Kansas that can work on my maximus? I just don’t want to send it through the mail.

    • Nomadgd
      Like Chris said.

      What’s wrong?

      I live in metro east Illinois by St.Louis. I drive over there every day to work. Kansas is a bit far away.

      But explain whats wrong. Thwre is a lot of us on the blog that mess with the Crosman/Benjamin guns. Plus we even change them around to personalize them.

      You definitely came to the right place to find out.

    • Nomadgd,

      If you describe what is wrong and have any mechanical ability you can fix it. Describe the problem, most folks here love to work on an airgun problem.

      If you are going to work on you Maximus MAKE SURE ALL THE AIR IS OUT OF IT. You can dry fire it till no more air comes out. It may be a simple problem.


    • Nomadgd,

      You may or may not have an actual problem, it could be that the check valve is dry and will not completly seal once the gun is filled. To correct this use Silicone Oil, this stuff here; /product/rws-air-chamber-lube-dropper-silicone-oil-50-oz?a=3002 do not use any petroleum based oil as petroleum based oil will detonate under high pressure. BY DETONATE I MEAN YOUR GUN MAY EXPLODE CAUSING PERSONAL HARM OR DEATH.

      Put some silicone oil in the fill nipple and fill the air chamber, you may have to do this a few times before you get the check valve clean and lubed, it should then hold pressure just fine.

      If that does not work the check valve may be damaged or excessively dirty, try this first and see how it goes.


        • Nomadgd
          Fill it up one more time.

          Then take some dishwashing detergent and mix some in some water and spray it all around the Foster fitting and also where the fitting screws into the tube.

          Then you should be able to see where its coming from.

          If it’s the Foster fitting you can buy a replacement pretty cheap from Pyramyd AIR.

          And just a reminder. Make sure you let (all) the air out of the gun before you start working on it.

          Let me know what you find out.

  18. BB,

    Thanks for covering big bores. A couple thoughts come to mind.
    1) we would benefit from another digit in the decimal place to describe the calibers.
    2) what is the common upper limit for big bores? 1/2 inch? Why stop there?

    • Whetor, to point #1……

      To me,… can the barrel makers hold bore size that tight?,… and can the slug makers hold slug size that tight?

      People (already) sort pellets for a reason.


      • Chris USA,

        As far as holding to that 0.000 tight tolerance sure for a price. Great link to barrel making by a small production Airgunsmith:


        You will see Dennis give you the maximum tightness he strives for. With other barrel making methods you can get varying degrees of tolerance but in the end it comes down to how much you spend and how tight the tolerance actually needs to be: Solid Copper, Steel, pure Lead, Lead alloy Bn XX, or clay ball.

        An example of that comes to mind…Slide Rules came in varying degrees of quality and K&E was the cat’s meow in my day. How did they achieve the accuracy, precision, and feel…they had a big number of rejects (sent to the burn bin) in every production run even with the high degree of initial input in materials, operators and production machinery.

        They were priced accordingly.


    • Whetor,

      “2) what is the common upper limit for big bores? 1/2 inch? Why stop there?” In the USA the BATF considers anything over .50 caliber (1/2 inch a Destructive Device) so a number of things are already in questionable territory.

      “Firearms Verification
      National Firearms Act Definitions
      Destructive Device
      26 U.S.C. § 5845(F)

      For the purposes of the National Firearms Act, the term “Destructive Device” means:

      Any type of weapon by whatever name known which will, or which may readily be converted to expel a projectile, by the action of an explosive or other propellant, the barrel or barrels of which have a bore greater than one-half inch in diameter.”


  19. Bore and Groove diameter question.
    You mention in the article to run a lead bullet .001″ over bore diameter.
    A .458 caliber rifle generally has a .450 bore diameter.
    So are you saying to run .451 diameter bullets?
    What prevents blow by, the bullet will not obdurate to fill the rifling groove.

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