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Pelletgage and the Speedy Pellet Inspector: new tools that can improve airgun accuracy.

Every firearm shooter who cares about tight groups knows that the size and shape of his bullets has a major impact on accuracy. But what about airgunners? What can they measure?

Until recently airgunners did not measure much of anything besides pellet weight. Some premium pellets are sold in tins of a specific head size, but until now all an airgunner could do is try each type of pellet, and each size head for those were listed, in hopes of finding what works best. Now there is a tool that allows us to measure the sizes of the heads of our pellets. And the question is--do pellet head sizes really matter that much?

Micrometers and Calipers Do Not Work

Right now some of you are thinking that a micrometer or caliper can be used to measure pellet head sizes. But this method doesn't work well. Measuring something as precise as the chord of a thin circle with a mike or caliper is dubious because it only gives the diameter at the point of contact. If the circle isn't perfect, there may be other places where the diameter varies. I saw that a lot in the testing I did while researching this article.

These measuring instruments also close their jaws with some force that can easily flatten the thin diameters of soft lead pellet heads. I admit the latter is not a great concern for a machinist who measures things with precision all the time, but it's a concern for the amateur who isn't that familiar with measuring malleable things like soft lead.

Introduction to the Pelletgage

The Pelletgage is a precision tool that lets you measure the pellet head sizes with speed and accuracy. The device is a metal plate with graduated holes that accept or reject pellet heads. If a hole accepts a head, the pellet falls through and will be caught on its skirt that is wider. The holes of the .177-caliber gage I tested are precision cut and range in size from 4.47mm to 4.56mm.

The Pelletgage does not change the size of the pellet. That is not its function. It measures the pellet head sizes so you can be sure they're consistent.

How It Works

You drop the pellet headfirst into the hole you wish to use, without pushing it. The instrument has a plastic plate above the precision steel gage plate to help guide the pellet head. If the head drops through the hole in the steel gage plate, you know that the pellet head has got to be that size or slightly smaller than that hole.

In truth, there is more to it. I find that if I rotate the base of the pellet lightly with the tip of my index finger while the head rests on top of the hole, the readings I get are more consistent and accurate. I start with a small hole and work up. For instance, if I'm measuring a pellet that's supposed to have a 4.51mm head, I'll start with the 4.50mm hole. If the head doesn't drop through, I move up to larger holes until it does. The first hole it drops through is the head size. In fact, to be able to drop through a hole the pellet head actually has to be a trifle smaller than the hole, but these holes are so precisely cut that we can use their sizes as absolute measurements.

If I don't know the head size of the pellet to be measured, I start small and gradually increase until it drops through. For example, I discovered that. 177 RWS Superdome pellets have 4.51mm heads, according to my gauge. And I also found they're very uniform. I measured 10 pellets for this report, and all 10 failed to pass through the 4.50mm hole but did pass through the 4.51mm hole. They are unmarked on the tin, but with the Pelletgage I now know what size they are.

You might think that will happen with every pellet, so I also tested H&N Baracuda Match pellets that are supposed to have 4.52mm heads. They were also very uniform, but the gage measured their heads at 4.54mm instead of 4.52mm.

I then measured 10 .177-caliber Beeman Devastator pellets. Three of them measured 4.51mm, four measured 4.53mm and the last three measured 4.54mm. None measured 4.52mm. From 4.51mm to 4.54mm is a wide variation! We need to give that that some thought. More on this in a bit.

How Can the Pelletgage Be Used?

1. Sorting pellets by head size. Airgun target shooters have proven that pellet head size affects accuracy. You will see tests demonstrating that in a moment. The Pelletgage allows you to find pellets with the same size head. Some tins say the pellets inside have heads that are all one size, but my testing proved that wrong. With the Pelletgage you'll always know for sure. Combine this with sorting each pellet by weight and you will have a very uniform batch of ammunition.

Think that's going too far? I can tell you with certainty that is exactly what champions do. Those who don't do things like this are the also-rans.

2. Finding the head sizes of pellets whose sizes are not marked on their containers. I have already done this with the RWS Superdomes that were mentioned above, and now know they have heads that measure 4.51mm--according to my gage. If you have an airgun that prefers pellets with certain-sized heads, the gage is a way to discover potential candidates without shooting every pellet in your inventory. Until now you may not have known your airgun had a preference for a certain head size, but the Pelletgage will reveal that.

3. Verifying the head size that's marked on the tin. I've already told you about H&N Baracuda Match pellets whose heads are supposed to be 4.52mm. The gage says they're 4.54mm. It also says their heads are very uniform.

Okay, my gage doesn't agree with the head size measurements from H&N. That really doesn't matter to me, but it's nice to know. Is the gage off a bit? Maybe so, but is it off as much as 0.02mm? Probably not, as you'll shortly discover. The equipment that was used to make the gage is far more precise than that.

4. Comparing one tin of pellets to another tin of the same pellets. As pellets are made, the dies used to swage them wear. Eventually, the die cavities open up and the dimensions of the pellets change. Do the pellets in the tin you just bought have the same size heads as the pellets you bought a year ago? The Pelletgage will tell you.

How Accurate is the Pelletgage?

Accuracy in a precision measuring tool is always a concern. The Pelletgage is manufactured with a diode-pumped fiber laser, using oxygen process gas to produce cuts that are very smooth. This laser cuts to an accuracy of better than 2 microns (one micron is one-millionth of a meter and one-thousandth of a millimeter) with repeatability. The holes vary in graduated sizes that are 5 times greater (the 0.01mm step between gage holes is 10 microns) than the accuracy of the cut. I mentioned before that the Pelletgage could not be so much as 0.02mm off in its measurement and this is the reason why.

Still, the Pelletgage maker, Jerry Cupples, is concerned with the accuracy of the finished gages. He checks the size of the finished holes with precision pin gauges, and doesn't stop there. Jerry photographed the edge of a similar hole (not from the Pelletgage) with an electron microscope and found that even when he slowed the laser cutter down, the holes still emerged with rough edges--but that's "rough" at a microscopic level.

As a user I'm not concerned with the Pelletgage's accuracy. In other words, I'm not concerned if the 4.51mm hole is not 4.51 mm exactly. If I were a pellet manufacturer using a Pelletgage to determine head sizes that I planned to print on my tins, then I would be concerned if the gage measured exactly 4.51mm.

As a user of the gage, though, I'm more concerned with the consistency of the pellets I measure than with their exact size. Once I learn what size head works best in a certain rifle, all I have to do is sort pellets and retain all those with that size head for that one airgun.

A pellet that gages 4.50mm today will gage 4.50mm tomorrow--even if it says 4.51mm on the gage. My concern is consistency, not the actual size, because I want all my pellets to have heads of the same size.

What concerns me is when I get pellets with three different head sizes out of one tin, like the Beeman Devastator pellets we looked at earlier, for example. They had three different head sizes that spanned 0.04 millimeters. That is a problem--with the pellets, not with the gage.

Measuring Technique

We're talking about such small tolerances that the pellets do not automatically fall into the gage holes--even with the clear plastic guide holes. Go back and look at the image of the magnified holes to see why. To sort them correctly, you need a technique. I had to wobble the base of the pellet around the gage hole lightly to get it to line up. That wobbled the head, in turn, and overcame the microscopic roughness around the circumference of the hole. I worried about wearing the edge of the pellets' heads by doing this, but I used an extremely soft touch.

I don't know if I caused any wear, but I was able to take a pellet of a known size back to the gage repeatedly, and it never measured any smaller from wear to the edge of its head. So, I think I'm doing it right. Time will tell.

Is the Pelletgage Necessary?

You've lived this long without one. How necessary is the Pelletgage? If you're a plinker who's content to reach into a tin of pellets and pull out whatever comes next--like me--then you don't need a Pelletgage at all. If you're a field target competitor who hopes to win a match, this might be something to consider. If you're a 10-meter target shooter who competes in national matches like I used to, then you almost have to measure head sizes.

We're just starting to know this tool, so its full importance cannot be accurately estimated at this time. I can make a case for this being the most important advancement in airgunning in the past decade, but until time passes and competitors have a chance to use it we won't know that for certain.

I can see vast potential for advances in precision. My guess is the Pelletgage will make a difference for some kinds of shooting, but not for all of them. There will be some folks who will swear by it and other folks who won't give it a second thought. I tested the Pelletgage to find out who those folks should be.

Testing the Pelletgage

We may agree that the Pelletgage works if there is a demonstrable difference in accuracy between the same pellets with different head sizes shot from the same gun under the same conditions. If this difference can be achieved using a youth model target rifle, the Pelletgage will have proven its value to competition shooters.

More than one million youth shooters compete in over 74,000 clubs around the U.S. each year, according to the NRA. Their goal is to work up the ladder to the NRA National Championships. A few of these kids go on to join the U.S. Olympic Team and many more are given scholarships at universities around the nation. The rewards for winning are both real and life changing.

The NRA has two classes of competition for young people--Sporter class and Precision class. The Sporter class uses rifles that are constrained to a low price ceiling that's considered affordable to clubs and individuals. Precision class shooters use the same rifles that are used in the World Cup matches and in the Olympics, where cost is not an issue. There are many times more Sporterclass shooters competing each year, and the best of them compete to gain the skill necessary to move up to the Precision class.

One Sporter-class rifle they use is Crosman's Challenger PCP. That was the rifle I selected for my first test.

Cheap Pellets

The youth marksmanship clubs are given huge discounts on pellets and even given some free pellets by both Daisy and Crosman. So, that is what they shoot. Why spend $15 on 200 world-class pellets when pellets are provided to them by their club for free?

The shooters train and compete with those pellets. The question is--can sorting them with the Pelletgage produce results?

I selected Crosman's Premier Super Match wadcutter pellet for my test. All shooters must use wadcutter pellets, according to the rules, because wadcutters cut perfectly round holes in official target paper, making them easy to score.

I first sorted 32 pellets by head size, using the Pelletgage. They turned out to have heads that were either 4.50mm or 4.51mm diameter. Out of 32 pellets, I found nothing other than those two sizes, which is very consistent. I stood them on their heads so the bases could be examined closely for flaws. None were found. There were 17 pellets with 4.50mm heads and 15 with 4.51mm heads.

Thirty pellets were then put into three lots of 10. One lot had all 4.50mm heads, another lot had all 4.51mm heads and the last lot had five pellets of each size.

Test 1. Youth Program Pellets

Then I shot these 30 pellets. The range was 10 meters, and I shot off a sandbag rest. I didn't care where on the target the pellets went--just how tightly they grouped.

I shot one target each with 10 pellets of all the same head size and one target with five of each head size.

Discussion of the Three Targets

Clearly, there's a big difference between the results of the 4.50mm heads and the 4.51mm heads. There's also a significant difference between the 4.51mm heads and the target that was shot with an equal mix of both head sizes. That target represents what will happen when the pellets are taken directly from the tin without regard for the head sizes. Right here youth shooting program coaches can see point gains of 5 points per match per shooter! And I'm being extremely conservative with that estimate. Your best shooters will gain close to 10 points per 40-shot match by shooting pellets with the ideal head size.

Now, for the tough question. Why is the group of 4.50mm pellets larger than the mixed group? If I had to guess, I would say that while 4.50mm pellets are less accurate, some of them do go to the same place as the 4.51mm pellets. Just not all of them, which is illustrated by the target on the left.

There were absolutely no called bad shots in this test. All shots broke with the bull centered in the front sight aperture.

These results are from one specific Crosman Challenger PCP target rifle. Other rifles, including other Challengers, may prefer the pellets that have 4.50mm heads. That's something that has to be tested for each rifle.

Coaches--Pay Attention!

This test has just demonstrated how to take those bargain pellets that are provided either free or at very low cost and sort them into something that will make more points for your shooters. If I were involved with a youth shooting program of any kind, I would get a Pelletgage, post haste!

Test 2. Testing a Higher Powered Gun

Do head sizes matter with airguns of higher power? Field target competitors shoot guns of much greater power than 10-meter target rifles.

For this test I shot 7.9-grain Crosman Premier lite pellets from my TX200 Mark III underlever rifle at targets 25 yards away. I know this rifle likes the Premier lite pellet, and I thought this would be another good test for the gage.

Because I had no idea how uniform Premier Lite pellets are, the first task was to sort them and see what I got. As it turns out, Premier Lites that Crosman packs in the premium cardboard box are very uniform. Most had a head size of 4.54mm. But every once in a while, I got one that was smaller or larger. They only differed by 0.01mm each way. At the end of my task, I had 111 pellets with 4.54mm heads, 11 with 4.53mm heads and 10 with 4.55mm heads.

I shot three 10-shot groups at 25 yards off a bag rest. I know from experience that this rifle does well when rested that way. There would be one 10-shot group with each pellet head size--4.53mm. 4.54mm and 4.55mm.

The Difference is Obvious!

Just like the target pellet groups, these three groups speak for themselves. Clearly, the 4.53mm pellet used to shoot the center group is far and away the most accurate pellet in this rifle. Because there are 10 shots in each group, we don't need to fool with average group sizes. With 10 shots, if a pellet is going to stray from the group--it will!

The group on the left with the 4.54mm heads is by far the worst group. Since the rifle was resting directly on a sandbag, no special shooting technique was involved and the rifle was fired the same way every time. This is how the pellet actually groups.

The 4.55 mm heads on the right made a 10-shot group that is almost double the size of the center group. So there is clearly a difference in accuracy between these two head sizes, as well. But shoot them all at a target without checking the head sizes first, and the resulting group will probably look okay, even though it'll be much larger than it could be if only the best group of pellets was used.

Note the small changes in the point of impact as the head sizes changed. Remember folks--these are all the same pellets that came from a single box! The only difference is their head size, which we wouldn't know without the Pelletgage.

Other Calibers Available

I've concentrated on .177 caliber in this article, but the Pelletgage also comes in .20 (5 mm), .22, .25 and .30 calibers. Those gages do exactly the same job as the gage we have examined, but pellets in those calibers are subject to far more variation than .177 caliber pellets. You need a gage for pellets in those calibers at least as much as you need one in . 177, and probably more. [Com. to page 86j

Hunters are a group who might use this tool. Hunters tend to shoot at extreme distances for an airgun, and they need all the accuracy they can get. And the larger calibers are the ones most often chosen by hunters, while .177 is universally chosen for competition in sports like bullseye target shooting, field target and airgun silhouette.

I think the Pelletgage inventor, Jerry Cupples, is due some congratulations for what he's done. He's given us a precision gage for sorting pellets that really does affect accuracy.

Speedy Pellet Inspector

Another instrument to help check pellets is the Speedy Pellet Inspector. It was developed by Joe Peacock, a friend of Jerry Cupples. This tool was actually invented before the Pelletgage and was the inspiration for the other invention.

The Speedy Pellet Inspector is not a measuring tool. It simply speeds up the procedure of inspecting the skirts of pellets. This is a task most competitors already do one way or another, so it is familiar to serious shooters.

Lead Pellets Are Prone to Damage

The best premium pellets are made from lead that is almost completely pure. Just a trace amount of antimony is alloyed with the lead--not to harden it, for hardness is the last thing we want. The antimony makes the lead form better when swaged from a blank into a pellet.

We want the lead in pellets to be soft and nearly pure because pure lead offers less resistance to the shallow rifling in an airgun bore. Those who shoot muzzleloading rifles know that soft lead leaves their bore cleaner and is more uniform and accurate than hard lead alloy. Pure lead has a self-lubricating property that slips through a rifled barrel with ease. But bullet metal that is soft comes with a problem. It deforms easily.

Diabolo pellets are hollow by design. They have flared skirts that obturate the bore, sealing compressed air behind them. Those skirts are thin and because they are made of soft lead, they are easily damaged. Even traveling in a pellet tin it's possible for a pellet skirt to be damaged.

For decades match shooters have used pellet boxes that display all their pellets skirt-up, making a quick examination easy. No measurement is involved. You can tell just by looking if a pellet skirt has been damaged.

World-class shooters only use pellets that come prepackaged in plastic trays, making visual inspection easy. These pellets sell for more than a lot of .22 rimfire ammo, but when World Cup and Olympic medals are on the line, who cares? Besides, nearly all these shooters are supplied their ammo by the pellet manufactures, so they really don't notice the cost. Shooters at the regional and even the national level, however, must still buy their pellets. It's expensive, but if they don't use the best they will never advance. So, one way or another, pellet skirts get examined by serious target shooters.

But in all other airgun sports, pellets are taken directly from bulk tins, where damaged skirts are a given. These shooters have been examining their pellets one at a time at loading, if they bothered to examine at all. Now they have the Speedy Pellet Inspector.

How It Works

The Speedy Pellet Inspector works by dumping a generous portion of pellets onto the plate and shaking the device. Most of the pellets will enter the plate nose-first, exposing their skirts for inspection. The remainder are spread manually.

Because I compete, I'm very familiar with the concept of inspecting pellet skirts. It is as common for airgun competitors as is the inspection of the overall length of reloaded ammunition for a reloader who is going for accuracy. But most shooters don't give it a second thought. They buy a tin of pellets, assume they are all perfect and start shooting.

Another party besides shooters is also interested. Pellet manufacturers are interested in the uniformity of their pellet skirts. I'm not talking about the makers of bargain pellets that you purchase at discount stores. I'm talking about pellets that cost $12 and more for 500. Premium makers like JSB do examine the skirts of their top-of-the-line ammunition.

Funny Thing

I was writing a short report for my daily blog at Pyramyd Air about how H&N makes pellets, and I was using some photos they provided. Two of them showed an employee using a device identical to the Speedy Pellet Inspector, but much larger. They use this device for all their hand-sorted pellets.


The Pelletgage and Speedy Pellet Inspector are both useful tools for the airgunner who wants to do his best. They take a lot of the guesswork out of the ammunition.

I'm convinced from my tests that pellet head sizes do affect accuracy in many airguns. The higher the quality of the gun, the more it will respond to ammunition of the correct size. For competitors, the payoff comes in the form of higher scores. The Pelletgage gives shooters a convenient way of sorting their pellets to realize this benefit.

The Speedy Pellet Inspector simply streamlines a process that most serious airgunners already do. I've been doing it for many years. Right now it's done just before loading each pellet, but with this tool a shooter can sort an entire batch before going shooting.

No, you don't need either of these items to shoot and enjoy your airgun. But if you want to win gold, you probably do.


My thanks for Jerry Cupples who provided the Pelletgages I tested for this article. He also provided some of the technical photos that I couldn't have gotten elsewhere. See his complete line of products on his website www.

Thanks are also due to Joe Peacock who developed the Speedy Pellet Inspector and provided one for my evaluation, as well as photos. To see all his products go online to
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Author:Gaylord, Tom
Publication:Firearms News
Date:Jan 20, 2016
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