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Education / Training Pellets’ fit in the bore: Part 2

Pellets’ fit in the bore: Part 2

by B.B. Pelletier

Part 1

Well, well! There’s lots of interest in this subject, and some of you have already made some observations of your own. Apparently, many people know that all pellets and bullets leak gas/air.

We left off with a discussion about thin-skirted pellets made from soft lead (which I often refer to as pure lead). Let’s shift to pellets with thicker skirts, and pellets made of hard lead. All Crosman pellets spring to mind when I mention hard lead. The Crosman Premier domed pellet in the cardboard box is still one of the best pellets on the market – BUT ONLY WHEN IT FITS THE BORE WELL. In the case of the Mendoza RM 2000, it is too loose at the breech, and the air is not sufficient to deform that hard lead skirt. For that rifle, the Premier is not the pellet to choose. That’s why I went with the Eley Wasp. That’s also the reason I used the Beeman Kodiak…to give you a pellet you can buy.

Crosman Premier skirt wall is thicker than the RWS Superpoint, plus it’s made of harder lead.

Kodiaks are fatter pellets, and they also have thicker skirts. So they fit well in larger bores, and they don’t deform easily. Premiers don’t deform easily either, but they are smaller, so you need to check the fit in the bore.

Not only is the Kodiak skirt thick at the end, it tapers to much thicker very quickly.

This is one reason why I don’t like repeating airguns. Guns with clips that have chambers smaller than the bore of the rifle allow the pellet to expand to that smaller size, then they enter the larger bore and rattle all the way through. If the clips have chambers larger than the bore, this isn’t a problem. There are things the manufacturers can do to correct this, with a choked barrel being one of the best. If they don’t do something, the rifle can never be accurate.

While this sounds like a terrible problem, most airguns don’t have it, so perhaps it’s more theoretical than real. I just like to load the pellet directly into the breech myself.

Why solid “pellets” cannot work in today’s airguns
A solid pellet must be exactly the diameter of the grooves to seal as much of the gases as possible, because pellets do not obturate. Big word, there. Obturate. It means to stop up or to close. In vintage blackpowder arms, lead bullets expand at their base when smacked by the force of the black powder exploding, and they obturate the bore when they do. In modern guns, smokeless gunpowder doesn’t burn fast enough to obturate a lead bullet as well as black powder, so the bullets must seal the bore with the diameter of their bodies. Airguns do not obturate bullets or solid pellets at all.

Because pellets do not obturate, the hole at the base of this piledriver pellet cannot cause the thick skirt to expand. This pellet must either fit the bore exactly or your thumb becomes a short starter! They are next to impossible to load in most breechloading air rifles.

The makers of solid pellets have to make their pellets to a certain diameter, then hope that the barrels they will be used in will have groove diameters close to the same size. They rarely do! Even different barrels of the same caliber from the same premium maker, such as Lothar Walther, will vary by several ten-thousandths of an inch in groove diameter, because the tolerance depends on the spring rate (rebound rate) of the steel in the barrels and the speed at which the rifling button is pulled or pushed through. Therefore, it’s virtually impossible for a solid pellet to fit the barrel of a gun, except by chance. When it doesn’t fit exactly, it becomes very hard to force through!

Shooters who shoot muzzleloaders use a wooden dowel, called a short starter, to hammer the bullet through the rifling and bore for the first few inches. This is best done with a single smack of the hand, but anyone who has shot muzzleloaders very long will tell you it doesn’t always work the way it is supposed to.

Well, when you try to load a solid pellet into the bore of an air rifle, your thumb has to be the short starter. After five pellets, you give up because of a painful thumb – that is, if you make it that far! If you own a rifle with a cylinder like an AR6, you just drop the solid pellets into the chambers of the cylinder, assuming they fit, and you’re done! The rifle’s air will do the work of sizing the pellet and engraving the rifling for you.

What about diabolo pellets that don’t seat in the barrel?
Your problem here is similar to the one of using a solid pellet. Some diabolos, such as Eun Jins, are very fat and don’t fit well into the bore of the gun. But look what kind of airguns they were designed for – the Korean guns! And most of them either have a cylinder or a linear magazine. The shooter never tries to force the pellet into the barrel. When you try to use them in an RWS Diana 34 Panther, they surprise you by being difficult to chamber. That makes them the wrong pellets for that rifle, in my book.

What about other pellets that do go in the barrel but their skirts stick out? If the gun is a breakbarrel or any sort of spring gun, I just shoot them anyway. However, if you open the barrel after closing it, you’ll often see that the pellet skirt has been smashed on one side. Don’t expect good accuracy from that pellet.

If your rifle is an AirForce gun, you run the risk of jamming the valve open and exhausting all the air in the tank! AirForce guns must have their pellets seated at least flush with the breech to function properly. Otherwise, they can mash a skirt to one side over the breech, locking it in place and causing a stoppage in the breech that holds the firing valve open. The .22 Condor is powerful enough to overcome this, but the .177 Condor is known for it. So, seat those pellets deep!

Does oiling pellets help seal them?
Let’s be clear – I’m not sure we need to seal pellets any better than they are sealed through normal handling. That said, would oiling them help? I don’t know, but I think not. I think the air passageways around the pellet are so large the oil will be blown off by the force of the air. Also, every time I have compared oiled pellets to dry, the oiled ones were slightly slower. But, again, I don’t know.

What should you look for?
This is not an exercise where micrometers are needed. Accuracy is the best way of knowing if a pellet fits well in the bore of a gun. Also, pay attention to how the gun behaves – especially if it’s a springer. Springers are temperamental about the pellets they prefer and will tell you with excess vibration, recoil and detonations when things aren’t right. Pay attention to how the pellet fits in the breech. These are the things that pay off downrange.

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

33 thoughts on “Pellets’ fit in the bore: Part 2”

  1. BB ,

    ” What about other pellets that do go in the barrel but their skirts stick out? ….. Don’t expect good accuracy from that pellet.”

    I totally agree with that statement. It’s been on my mind for sometime. The breakbarrels might deform the skirt EVEN WHEN THE BARREL IS SNAPPED SHUT. Accuracy might suffer.

    Worst thing is, it seems to me like a case of being trapped between the devil and the deep sea. If the skirt sticks out, accuracy may suffer for the reasons given above, but IT DOES HELP HOLD THE PELLET TILL GOOD BREECH PRESSURE IS REACHED. If the skirt was flush into the bore, I think breech pressure might suffer as the pellet would start moving much earlier.

    Your comments on this ?

  2. BB,

    whats the difference between the UTG m14 and the TSD M14???

    In terms of performance and the gun itself and not in the accesories.


    Hernan (CF-X guy)

  3. I was shooting my Diana 48 a while back using Beeman Kodiaks (.22, 21 gr?). They caused the rifle to kick harder than usuall. I think this was caused by piston bounce. You might have said it a while back, but isn’t that bad for springs?


  4. BB.

    I know this is off.topic but im new to the world of scopes and i was wondering. If a scope says 6-24×56, does it mean that you can only use it at 6x and 24x, or you can also use it anywhere in between.


  5. Hernan,

    I haven’t tested the TSD M14, but a look at the numbers tells me it has about the same power as the UTG.

    Of course the TSD is just a manual spring gun, so you can’t walk the rounds into the target the way you can with the UTG. With an AEG, that’s half the fun!

    As for accuracy, who can say without a test?


  6. I could shoot myself in the head for wasteing the whole day tuning my Diana 46E. I had the springs and 2 new seals for 2 rifles I was going to work on. Everything came apart and went back together smoothly. Except for the part where I put the piston seal on. The sharp edge on the top of the piston chewed up a brand new seal ($19). I took the edge off with 800 grit sandpaper and applied a little moly to help it slip on a little easier and used a small flat head screwdriver to pull it gently around the edge. The 2nd seal went on perfect. Applied all the moly and tar and put it back together. Fired five shots outside since it would probably smoke a bit. It detonated a couple times. Took it inside to the little indoor range to test it. First couple of shots it dieseled a little. Then the kicker came when I noticed a little piece of yellowish silver in the loading port. Hahahaha, it was a piece of seal. The really funny part is that the new spring and seal changed little or nothing. It has exactly the same velocity and power. I wanted 12 or 13 ft lbs but have the same old 9 or 10. After wasteing $70 on a spring kit, $40 on seals and a whole day, I’m officialy ticked. I don’t plan on touching my Diana 48 for fear of this repeating itself. It seems everything I do lately turns out this way lol. I guess I’ll have to put the factory seal back on and see what happens.


  7. BB,

    I really want to order from pyramidair.The thing is they have hreat prices but when it comes to shipping its too expensive.I live in Puerto Rico and the shipping is too high.The price of the item is good but when you add shipping is more expensive than many other companies.Can pyramidair ship via USPS or something cheaper?
    Like I sayed,I really want to buy from them but the shipping is way too much.And I dont get free shipping I have to pay abouy 45 USD fo a airsoft rifle wich is too much.Thanks I will apreciate your help.


  8. Shawn,

    Some people use heat like from a hair dryer to soften up the piston seal and Maccari says to spin the seal around to make sure its true. I didn’t use any lube on the piston dovetail but I did hit it up with some 220 wetordry. I think the main reason a seal gets chewed up is from going past the cocking slot. Use a small file or sandpaper or both on the cocking slot and a tool to help get your seal past it. A thin layer of clear tar help also.

    The main reason to tune a gun is to make it shoot smoother.

    I just did a lube tune , heat shrink on the spring guides, new seal, and put in a trigger insert on a Gamo shadow 1k. Its shooting like a different beast(no more buzz,quiet, powerful) and cost me $24 for the supplies. Next I will be thinking of custom guides and springs for my other gs1k.

  9. Shawn,

    I don’t know if a stronger spring will increase the power of my s1k or if I really need more power out of it for what I use it for.
    The stroke would stay the same as far as I know so power gains would be limited.

  10. B.B. if solid “pellets” (realy bullets) don’t work well in an air gun, then why do big bore airguns use bullets?

    Does it have to due with the amount of airflow or power in a big bore tha offsets any isssues that would occurr with a typical airgun?

    I would like to know why if possible thanks!

  11. RTyan,

    The reason big bores work with bullets is their twist rate is fast enough to stabilize their larger bullets. The larger an object is, the slower it has to spin to stabilize. The earth, for instance, spins once in 24 hours.

    The twist rate for the .22 caliber M16 is 1:9 (some are as fast as 1:7). A .30 caliber rifle needs 1:10. A .45 caliber rifle needs 1:18-1:22, depending on the bullet weight and velocity.



  12. It made it past the cocking slot just fine. I babied it past all the edges even though I smoothed them over beforehand. I think it might just be a bad batch of seals or something. The factory seal feels a lot sturdier than the yellow Tesla seals I got from Maccari. I really wanted to get about 12-13 ft lbs out of this rifle, something in the neighborhood of a HW-77/97. I consider it a complete failure.


  13. I just thought of something while stewing in my self loathing. Like you said cyberskin, the stroke would be the same even with a new spring. I know there isn’t that much difference between a model 46 and a model 48. The spring kits are basicly the same. What makes one produce say 10 ft lbs and the other 16 or so in .177? Probably the length of the piston’s compression chamber and the weight of the piston. I know for a fact that the piston in my 46E is heavy and a good 8 inches long. I saw a picture of a model 48’s piston not long ago. It looks tiny in comparison and I’ll bet it’s shorter and lighter. I wonder if a regular model 46 has a lighter piston that would work in my rifle? I’ll have to measure the weight of my piston and measure the length and ask Pyramid for the dimentions. They sell spare parts. Let’s see if this works. Mwahahaha.


  14. Ya and even if it did pull back the shorter piston, the seal might be pulled out of the compression chamber. First shot the seal get ripped on an edge.

    I’ll take a look at my 48 Monday when I have a day off. I’m on call for Federal jury duty for 6 weeks so work has me scheduled off on Mondays. Yay, I get to work Sundays. Yet another reason I think I’m cursed. Anyhow, I realise they are all set up different and most parts are not interchangeable. Even if they where, replacement parts are expensive. Pistons for a model 48 are $45.


  15. I took the model 46E back apart again tonight. It gets easier every time. Slipped the spring and piston back out. I feel like a huge dummy. The seal outer rim was still intact. The inner diameter where it is held down by the dovetail was split in several places from detonation. Lesson learned: never use a lubricant to slip seals on the piston head. And always take the sharp edge off the dovetail. That’s what killed the first seal.

    As I was thinking about this, I realised something. It’s a model 46E. It seems to only produce 9.75 ft lbs whereas a 46 produces 13 or so. Hmmm. I got it at a good price. Could it be a European model someone dumped on the American market to get rid of them? Why yes by jove I think you’re right. Still a nice rifle though.

    I believe it’s the heavy piston in this thing that reduces it’s power. Pyramid Air doesn’t have replacement pistons for the model 46 so I wrote to Umerex. Hopefully they have them. It seems they no longer list this rifle among their offerings for RWS so I assume they have discontinued it.

    Thanks for everyone’s help and suggestions with this.


  16. BB-
    Why is it that some pellets such as the gamo hunter are groved whereas some, such as the crosman premier and beeman kodiak are smooth? Is there any advantage to grooving? If so why don’t the more expensive pellets have them? Thanks

  17. BB
    I am soon to acquire an old pellet rifle from someone who said it has been sitting in his closet for 25 years. Obviously, I’ll have to take care with checking it over and oiling the (most likely) leather seals. He says it’s probably a .22 caliber and he describes that it used solid pellets/bullets. Is there any way of telling what type and weight of ammo this weapon would take if it is not specified? JP

  18. JP,

    Sounds interesting, but impossible to tell what it is from the description. You could always hope for a Weihrauch HW54EL, otherwise known as the Barakuda. It could also be a Benjamin 3120. Both those rifles use .22 round balls.


  19. Hey B.B. –

    I have been looking for a relevant place to place this comment and this post seems good.
    I have a Gamo MultiShot rifle with an eight shot magazine. Up until recently everything has been working (for the most part) flawlessly. Recently however, I have been having trouble with my magazine jamming. After the 2nd shot, the rotary magazine travels in between the 3rd and 4th shot. Thus, when I pull the trigger, neither the third nor fourth pellet travels down the barrel, but rather they get stuck towards the end of the magazine. I am not sure if this is a problem with my magazine or if it is a problem with my gun when it is rotating the magazine. If you need some more clarification, I can get you some photos of my problem by next wednesday (a family member who is currently on a trip is borrowing my camera until then).

    Many Thanks,

    p.s. If you need some information on my Gamo Multishot:

  20. Mike,

    Your pawl is mis-timed. This can be due to wear or to foreign matter in the pawl-ratchet mechanism.

    I think a pellet fragment is embedded in the ratchet wheel, causing the feed pawl to advance the clip past the index point.

    The solution is to locate the foreign matter and remove it.


  21. B.B.

    I am assuming that the “pawl” is the part of my gun that advances the magazine to the next pellet. Is this correct? Also, where is the “ratchet wheel”? Is that within the magazine? Sorry, I am not very good with all of the terms. So, if it is possible to rephrase and/or just state the definitions of the terminology that you used, that would be greatly appreciated.

    Many Thanks,

  22. Mike,

    I’m not familiar with this model rifle, but you say it has a rotary magazine. I changed that to a rotary clip, which is the name if the device comes out of the gun. If it stays in, it’s a magazine.

    A revolver cylinder, which is what you have if it’s rotary, is advanced by a pawl, which is a steel rod that bears against a toothed ratchet wheel. The ratchet is a crown-shaped piece of metal that catches the pawl and resists it, resulting in the rotation of the clip on its axis when the pawl pushes. The ratchet will be part of the clip, itself. Look there for a piece of lead that is smashed into the ratchet teeth.


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