Ammo Nation! As a country of airgun shooters, we’re spoilt for choice when it comes to our ammunition. Mike Morton offers some pointers to help you pick your perfect pellet
Whenever you take a shot with your airgun, you have one objective in mind – to place your pellet at a specific point on your chosen target with as much precision and little margin of error as possible. In the case of a scoped rifle, four elements come into play: the rifle itself, the scope, the mounts and the ammunition – and there can be no weak links in that chain if you are to obtain the best results possible. In terms of your ammo, three things need to be considered before you can even begin to explore the accuracy you crave: pellet calibre, pellet types and pellet weights.
In the UK, we are restricted to rifles with a muzzle energy of less than 12 foot pounds. If you want more power, you not only need to apply for a Firearm Certificate, but need to have a good reason for wanting more power as well. This means that in practical terms, four airgun calibres have established themselves for use in non-FAC, UK-legal air rifles: .177, .20, .22 and .25. All have their strengths and weaknesses, their supporters and detractors.
The .177 pellet, which has a metric measurement of 4.5mm, is the smallest-diameter pellet type in common use today. It is widely used for plinking, hunting and target shooting – and for some target disciplines, such as 10 Metre Air Rifle, it’s the only acceptable calibre.
Because the pellets are so small, they use less lead to make and are therefore usually cheaper than their larger-calibre counterparts. Because of their physical size, they are certainly more fiddly to handle when loading either directly into the breech of a springer or into the magazine of a multi-shot PCP. This is especially so for shooters with large hands. But what about accuracy?
Many people believe that a .177 pellet is more accurate than any other. That’s not actually true, but there are two possible reasons why that belief may have come about, the first being its flatter trajectory. Because a .177 pellet is lighter than a comparable .22 pellet of similar shape and design, the .177 pellet can be propelled faster from a sub-12ft lb rifle.
Muzzle energy is not the same as velocity: it’s a function of both pellet weight and speed, so a lighter pellet can travel faster than a heavier pellet while having the same muzzle energy. In the case of a fast-flying .177 pellet, that speed translates to a flatter trajectory, so there is less of a need to compensate for ballistic drop-off than with the .177’s larger, heavier and slower rivals. This, in turn, means it can be easier to more reliably place that pellet exactly where you want it, giving rise to the idea that .177 is indeed more accurate.
Another consideration is the fact that many rifles made for competition use will be produced in .177, again bolstering the idea that the smaller pellet is the most accurate calibre, when in reality it’s the higher velocity achievable from this calibre that lets the projectile be placed on target more easily than its counterparts – at least in terms of pellet drop and holdover.
One of the main arguments against the .177 pellet is its lower ballistic coefficient (BC) in comparison with a heavier pellet such as a .22, meaning the .22 should be better able to cope with crosswind while retaining more energy at longer distances. Another disadvantage of .177 for the hunter is the likelihood of over-penetration, which we’ll look at later.
While .20 should logically come second on our list in terms of ascending calibre size, it’s more useful to talk about .22 (5.5mm) now. The actual beginnings of both the .177 and the .22 are somewhat obscure, with different sources citing different countries of origin and year of introduction, but the .22 has long been associated with hunting as it was derived from the .22 rimfire calibre. A .22 calibre airgun pellet possesses a higher BC than a .177 pellet of similar shape, so in theory it should be the better all-round pellet, maintaining velocity as well as energy at range. But this is only true when it’s fired at higher velocities, as a pellet’s BC will change as it slows down, and we can’t achieve these velocities in .22 with our sub-12ft lb rifles here in the UK.
But while a .22 pellet can’t take full advantage of its higher BC, it does retain more energy at range than a similarly shaped .177 pellet, delivering more destructive force to the target. This means it hits harder and transmits more energy to live quarry than .177, making it a valid choice for the hunter and pest controller. The smaller .177 pellet will be flying faster, but the much smaller cross-section of its head means its destructive power will be applied to a very concentrated area on the animal.
This can be illustrated by an example my old physics teacher taught me at school. A lady wearing shoes with stiletto heels stands on a soft wood floor next to an elephant. Which one of them does more damage to the wooden floor? The woman will, due to the lighter but more concentrated force being applied through the stiletto heels to the wood underneath.
In a hunting scenario, it’s quite possible for a .177 pellet to pass right through a rabbit’s head, for example, potentially missing the brain and not delivering an instantaneous killing shot if all this energy isn’t reaching the right area. This is known as over-penetration. With a .22 pellet, more energy will be transferred into the quarry, resulting in a potentially cleaner kill. However, as already mentioned, the .177 flies flatter, so it’s easier to put that pellet on target in the first place. This is probably the crux of the ‘.177 vs .22’ debate: the .22’s ability to deliver a more telling, fatal shot compared with the relative ease of shot placement offered by the .177. It’s a debate that’s been raging for decades – and it certainly won’t be settled here!
An experienced shooter will have no problem allowing for holdover with a .22, but this calibre is nevertheless at somewhat of a disadvantage for target shooting compared with .177, so much so that a different class exists for .22 in some events. As for general shooting, .22 is great for plinking, and it’s usually easier to cock a .22 springer than a comparable .177. The .22 pellet is easier to load, due to its size, but will cost a bit more to buy.
The .20 pellet, which has a metric diameter of 5mm, is often termed the ‘compromise calibre’ as some shooters consider it to be a good balance between .177 and .22. Depending on the type of pellet chosen, this is certainly true in terms of weight, with a sample tin of Rangemaster Kaiser in my collection, for example, weighing 11.42 grains, compared with an average weight of 8 grains for a tin of .177 and 16 grains for a tin of .22.
Advocates of the .20 say that it flies flatter than a .22, while hitting harder than a .177, offering the best of both worlds. Detractors will argue it does neither job as well. Both of these observations are purely subjective; but a more objective observation is the fact that fewer rifles are available in .20 than either .177 or .22, and there is a much restricted choice of pellets, so while the .20 is capable of superb accuracy, it can be a harder journey to find the right pellet for your barrel.
.20 is most useful as a hunting calibre, although it can be shot in target competition as well, usually being positioned in the .177 class. Pellets cost roughly the same as .22.
This calibre is definitely one for the more seasoned shooter wanting to try something different. Shooters I’ve known (myself included) who’ve tried .20 typically either abandon it quickly or become life-long converts. It may be the compromise calibre, but there seems to be no happy medium in terms of its supporters!
Now we come to the biggest of the conventional airgun calibres – the .25, or 6.35mm in metric format. Whereas .177 and .22 are airgun stalwarts, both .20 and .25 do tend to fall in and out of fashion on a cyclical basis, but .25 is actually thought to pre-date .177, being introduced in the late 1800s, albeit in smoothbore airguns.
Because of its size and weight, .25 is the hardest-hitting of all four calibres, but when launched from a typical sub-12ft lb rifle its trajectory is the most loopy. As with .20 and .22, an increased need for holdover does not mean it’s an inaccurate pellet: it just means it’s harder to place the projectile on target, and the shooter’s holdover and range estimation skills must be impeccable to get the best from this beast of a pellet.
Because of its pronounced trajectory, shooters of this calibre tend to use it for close-range hunting and pest control work, typically focusing on rats, where the pellet’s loopy flightpath is less of a disadvantage, and its main advantage – the fact that it hits like a sledgehammer – can be fully exploited. However, for the hunter who’s prepared to thoroughly learn their pellet’s performance, .25 can make a good rabbiting round as well.
WHAT DOES BALLISTIC COEFFICIENT MEAN?
The ballistic coefficient (BC) of a pellet is a measure of its ability to overcome air resistance in flight. It’s stated as a decimal fraction smaller than one, with a pellet with a higher number, and therefore a higher BC, losing velocity more slowly – and therefore being able to fly further – than a pellet with a lower BC. A ballistic coefficient is a function of a projectile’s mass, diameter, drag coefficient and shape.
Long-range boat-tail bullets, which tend to be heavy, long and pointed, have a high BC, such as 0.36 for example, while pellets, especially the typical diabolo (waisted) shape, have a much lower BC, such as 0.03.
A BC isn’t a constant: the BCs of both lighter and heavier pellets will change in flight, but a pellet with a higher BC will maintain its edge over the pellet with a lower BC at any identical distance.
What does this mean in practice? Actually, not that much. Diabolo pellets are shaped like shuttlecocks for a reason. They are designed to fly relatively slowly, and their thin waists, flared skirts and hollow tails all contribute to a phenomenon known as obturation, where the pellet’s skirt, which is made of soft lead alloy, will fill up with air and flare out under the pressure of firing, filling the bore and engaging the lands of the rifling in the barrel.
The ability for a pellet to spin in flight and maintain stability at the relatively low velocities achievable from a sub-12 ft lb rifle is far more important than its ability to maintain a high BC.
USE YOUR HEAD
Some interesting pellet shapes have emerged over the years, including solid slugs and air bullets, but let’s concentrate on the diabolo pellet and its various types of head, as these are optimised for use in sub-12 foot pound guns.FLATHEAD: The flathead, also sometimes known as a ‘match’ or ‘wadcutter’ pellet, is designed for short-range competition for use on paper targets, typically 10 metres. The flat surface of the head cuts a cleaner hole in the target than any other pellet type, making scoring easier, while its poor flight characteristics don’t begin to manifest themselves at the close ranges at which these pellets are normally used. Some hunters like to use flatheads for short-range pest control, as the flat surface will impart more destructive energy than a domed or pointed design is capable of.
HOLLOWPOINT: The concept of the hollowpoint pellet, just like a hollowpoint bullet, is to make the head expand upon contact with the target, thus reducing the chance of over-penetration and maximising the destructive energy transfer. This makes the hollowpoint an out-and-out hunting and pest control pellet.
There are two main limitations, though. The expansion of a hollowpoint may not be as much as expected, depending on the terminal velocity of the pellet, the density of the target and the type of lead alloy from which the pellet has been made. Its other limitation is the fact that it has a flat, un-aerodynamic head, which means it may not fly too well much beyond 25 yards or so. Experimentation is key!
BALLISTIC-TIPPED HOLLOWPOINTS: There are some speciality hollowpoints, such as the RWS Power Ball and the Predator Polymag, that attempt to overcome the aerodynamic disadvantages of the standard hollowpoint pellet by filling in the hollow to make it fly better. The Power Ball uses a small ball bearing to achieve this, while the Polymag takes its inspiration from firearm cartridges such as those from bullet manufacturer Nosler, using a polymer cone to achieve better aerodynamics. In both cases, the idea is to help the pellet fly to its target more efficiently, while letting the head expand just like the regular hollowpoint upon impact. These are hunting rounds.
POINTED: The pointed pellet is another hunting design, but this time it’s meant to help a pellet penetrate further into the quarry animal – the antithesis of over-penetration. The pointed design may look aerodynamic, but these pellets don’t always fly well. This may be due to the fact that the tip may not be perfectly concentric to the mass of the pellet and the bore of the rifle. If this is the case, accuracy at range will be severely hampered as a result.
DOMEHEAD: We finally come to the domehead, sometimes called ‘roundhead’ pellet. This isn’t just a good all-rounder, it excels at most tasks asked of it – and will do it at distance too. The domehead is ballistically superior to all the other diabolo head types, meaning it will shoot more accurately over all normal airgun ranges than its rivals.
With the exception of certain types of target competition, where flatheads are mandatory, domeheads can be used for both target shooting and hunting, and are better at coping with crosswinds and maintaining velocity while they do so. It’s no surprise that the domehead is the pellet of choice for both HFT and FT.
WHAT’S MUZZLE ENERGY?
Muzzle energy is the kinetic energy of a pellet as it is fired from the muzzle of an airgun. It’s a measure of the destructive potential of the pellet, which is important for both hunting, where greater destruction of the target means a more humane kill, and for complying with the law – the legal limit in the UK being 12 foot pounds for a rifle and 6 foot pounds for a pistol.
To work out the muzzle energy of your gun, you’ll need a chronograph to find the muzzle velocity in feet per second. You’ll also need to know the weight of the pellet in grains. You can then use this formula:
Pellet weight x muzzle velocity x muzzle velocity ÷ 450,240
Let’s look at the example of a .177 pellet weighing 7.85 grains with a muzzle velocity of 798 feet per second.
7.85 x 798 x 798 ÷ 450240 = 11.1ft lb
Now let’s do the same for a .22 pellet weighing 16.2 grains with a muzzle velocity of 555 feet per second.
16.2 x 555 x 555 ÷ 450,240 = 11.1ft lb
In each case the muzzle velocity is significantly different, while the muzzle energy is identical, both being well within the law.
THE DIABOLO: IT’S DEVILISHLY GOOD
Despite its satanic-sounding name, the diabolo is an absolute godsend to shoot, and is the most common pellet in use today. It’s also known as a ‘waisted’ or ‘wasp-waist’ pellet, meaning the head tapers back to a thin section roughly half-way down, before it tapers out into a hollow skirt, a bit like two shuttlecocks meeting head-on.
The head, or front section, of the pellet will usually be sized to fit the bore for optimum accuracy, while the skirt may or not touch the lands (the raised portion of the rifling) when it’s inserted into the breech. Instead, the skirt will flare out on firing as part of a process called obturation, ensuring good contact with the lands from both the head and skirt, while keeping friction to a minimum because of the tapered design.
Diabolo pellets have been developed over many decades, and work best at subsonic velocities. If a diabolo goes transonic, turbulent air builds up behind the head, making the pellet unstable in flight and throwing away any chance of accuracy. Luckily, transonic flight is not achievable at the velocities generated by a sub-12ft lb rifle, so the diabolo shape is perfectly suited for all our non-FAC airgun needs. The diabolo even works well at lower FAC levels, although heavier or more specialist shapes of pellet will be more appropriate for higher power levels.
WEIGHING IT ALL UP
Diabolo pellets, regardless of their calibre or type of head, may be available in a range of different weights. In my collection of .177 pellets, for example, I have a tin of JSB Exact Express with an average weight of 7.9 grains, and a tin of H&N Baracuda Match, weighing 10.2 grains – that’s a difference of 22.5% within the same calibre. Heavier pellets are intended to better retain their energy at the expense of a more pronounced trajectory. Lighter pellets may have a greater muzzle velocity, but their energy will fall off more quickly. Which is best for you will – yet again – come down to experimentation, along with their intended use in your gun.
One of my rifles, for example, was serving dual duty a few years ago as both a target rifle and a hunting gun. It was broadly most comfortable with two pellets from H&N –
the above-mentioned Baracuda Match and the lighter FTT, which comes in at 9.0 grains. At 25 yards, which was my default target-shooting range at my club at the time, the FTT was the more accurate pellet. But when I pushed the range further – shooting out to 50 yards – the roles had reversed, with the Baracuda Match delivering a tighter group than its sibling.
In the end, pellet selection really comes down to three things and can be dealt with in relatively short shrift:
PICK YOUR CALIBRE: If you’re new to the sport, it’s best to limit your choice to between .177 and .22, understanding the pros and cons of both thoroughly before you experiment further. More seasoned shooters – particularly hunters – might like to give .20 or .25 a go.
PICK YOUR PELLET TYPE: While it’s fine – not to mention good fun – to experiment with other head types, you really can’t go wrong with a domehead for general shooting.
PICK YOUR PELLET WEIGHT: Have you heard the expression ‘your mileage may vary’? That’s what can happen here. By all means experiment with different weights within your chosen calibre, but ultimately I’d always pick the pellet that’s most accurate in my rifle, regardless of how light or heavy it is, when shot at its intended range.
So what is the perfect pellet? It’s the one that helps you hit your target most reliably at your chosen distance. Have fun experimenting to find the perfect pellet for you.