In the UK Air Rifles and Pistols are incredibly popular. This is largely down to three reasons. They are cheap to buy and run, they are ideal for dealing with common small pest species and last of all they are not as heavily regulated as section 1 firearms (power and location dependant). Many of us including myself use an Air Rifle for pest control on a regular basis. Target species such as Rats, Pigeon, Corvids and Rabbits are commonly dispatched. Most Pest Controllers are aware that nothing beats a well placed shot. However even well placed shots can produce sub par results if your projectile is not doing its job. In this article I will discuss terminal ballistics and its importance in being both an efficient and ethical hunter.
Terminal Ballistics refer to the final part of a projectiles flight at the point of impact on the chosen target and it’s affect on said target. I conduct controlled experiments in Terminal Ballistics as part of my day job in the Defence sector. As an Air Rifle shooter and hunter I was keen to find some viable data on Pellets and their terminal effect. What I found lacked any real control of variables so I thought I would conduct some tests myself.
There are some commonly accepted beliefs regarding the lethality of an Air Rifle Pellet. I have heard many people suggest pellet selection doesn’t matter. They simply buy what is locally available at a price point they like. I have heard people say they will buy the heaviest pellet available in their chosen caliber. After all a pellets potential kinetic energy is 0.5 X mass X velocity squared. In simple terms it should be heavy and fast.
A Suitable Projectile
So imagine we had a projectile that was heavy (in comparison to others in caliber class) but long and thin, a heavy dart in other words. Such a projectile would likely travel through an intended target using up only some of its available energy. The rest of its energy would be wasted. A large flat faced projectile would deliver much more energy without over penetrating but it would also be very poor at reaching the target due to such a poor drag factor.
Companies have come up with all kinds of exciting looking designs which seem to offer the ultimate in external ballistics and terminal effect. I am going to test some of the most popular pellets on the market right now with an aim to adding more as time goes on. This testing will focus on using a non FAC rated .177 rifle. I will conduct further tests in .22 and in FAC variants if the article generates enough interest. We can then make a comparison overall.
The testing uses 10% Porcine Ballistic Gelatin. This is made to a specified recipe which involves mixing dried Porcine Gelatin granules with hot water (140 degrees Fahrenheit). A few drops of Cinnamon oil are also added which aids gel clarity and reduces mould growth. I warn that this can put you off Cinnamon Swirls for life. The mixture requires a lot of stirring and constant removal of foam which rises to the surface. If you do not take care at this stage then you will end up with lots of air pockets and bubbles which affect calibration and visibility. The gel blocks take 2-3 days in the fridge to cure. They are callibrated using the following technique:
A .177 caliber (4.5 mm) steel BB to be fired from an air gun and hit the Gelatin block at 590fps +/- 15 fps. The steel BB must penetrate 8.5cm +/- 1cm into the gelatin block
Why Porcine Gelatin?
It is worth noting that the Porcine Gelatin produces very different results to the Clear Ballistics silicone blocks. This is due to the high water content in the Porcine variant. Clear ballistics are great for marketing shots but are not suitable for serious testing. I used my own BSA Ultra SE Rifle and achieved the correct velocity by running the tank on the gun low and firing BBs through some commercial Oehler Chronograph screens (also callibrated) until the desired velocity was reached.
The BSA Ultra was incredibly consistent even when the tank was low making this task a relatively easy one. I was able to achieve 8cm penetration at 597fps on the gel block. Once callibrated the block is said to be representative of muscle tissue and thus can be used for testing terminal effect in soft tissue.
Before firing into the Gelatin I refilled the tank on the BSA Ultra SE the recommended 232Bar. I will review the Ultra SE in a following article as it has proven to be a superb little rifle and ever so consistent. It also serves as a great yardstick for the first round of tests as it represents an Air Rifle that an average non FAC holding pest controller might use.
Once callibrated the Gelatin block was set up 10yds away from the rifle. This represents a “best case scenario” in terms of terminal velocity. Normally you target species would be between 20-30yds away when using a non FAC Air Rifle. However my current Ultra SE is running a little on the lean side of 12ftlbs energy. This is certainly not uncommon in the non FAC air rifle world as nobody wants to accidentally run into legal trouble. Some rifles will be nearer the upper limit of power which would equate to my velocities being more like a 25yd distance. In short it gives us a useable baseline for the first batch of testing.
I chose a cross section of pellets that I felt represented really popular options among air rifle shooters. H&N got a little bit more representation as I happened to have a few and they make fantastic hunting specific pellets. I also selected a couple of popular choices which are not specific to hunting and a very heavy pellet which people might imagine would improve the terminal effect.
1. Air Arms Diabolo Field 4.52mm 8.44gns
These are my go to pellets for accuracy. I have tested a lot of different pellets in my Air Rifle and these always make one ragged hole and 20yds. None of the other pellets I have tried produced unnaceptable hunting accuracy but then I have never tried any budget pellets. Maybe that is a test for another article. Air Arms make no claims about terminal effect but do suggest they are a popular choice among hunters. They are very consistent in weight and form and have a classic dome profile. The pellets weigh 8.44gns which makes them the joint 3rd heaviest pellet on test.
H&N Terminator 7.25gns
A really interesting design from H&N which they say offers superb expansion in non FAC guns. H&N suggest the point aids penetration though fur. For this test we will be shooting into bare Gelatin but a fur covering could certainly be used in future tests. The pellets are consistent in weight and form and offer good accuracy despite the strange design.
H&N Baracuda Hunter Extreme 9.57gns
The BHE pellets are a hollow point design. The front face of the pellet has a central void and there are cross cuts which are intended to aid expansion. These are the second heaviest pellet on test. H&N recommend a minimum of 12ft.lbs at the muzzle for the best performance. A very popular choice for Airgun hunters.
RWS Super H point 6.94gns
A very popular choice among hunters. These are the lightest pellets on test. The H point refers to a hollow point. These are consistent and shoot accurately. RWS suggest they offer a great balance between penetration and expansion.
RWS Super Field 8.33gns
Another very popular choice, the Super Field is intended for Field Target competition. They shoot very accurately and are reasonably priced so they inevitably get used for hunting.
JSB Exact 8.44gns
Another field target type pellet which has proven very accurate. The JSBs are consistent and incredibly popular. They are joint third in terms of weight. JSB have a number of hunting specific pellets but many hunters are just as happy to use the Exacts simply based on weight and it’s perceived benefit.
H&N Sniper Magnum 14.57gns
The heaviest of all the pellets tested here and the only “slug” variant. H&N suggest a 12ft.lbs minimum again which suggests these were really intended for FAC use. They shoot very consistently in my Rifle and accuracy is spot on despite their unusual form. These represent the choice of hunters who select the heaviest pellets because they think that increases “knock down power”.
Once the block had been shot with each pellet I sectioned it. This will allow us to make comparisons and inject each wound channel with some blue dye so we can see them clearly. Let’s first compare penetration depth. There are no legal and appropriate target species that require really deep penetration. To much penetration just means exiting the intended target and wasting kinetic energy.
We can see in the picture above that three of the hunting specific pellets stopped between 3-4 inches. The field target pellets and the heavy Sniper Magnums finished at around 7 inches. In my opinion the 3-4″ penetration depth would be ideal. You must always slightly over compensate penetration depth in gel because it doesn’t realistically represent fur, bone and so on. 7 inches in my opinion is too much and kinetic energy will be wasted when the pellet exits the target.
The AA field has caused a small amount of tissue disruption in the first inch of penetration. After that the wound channel shrinks to the point that the dye will not fill it. This is not a very desirable terminal effect but with good shot placement they would still do the job.
We can see why the wound cavity was poor from the photo taken after the pellets had been removed from the Gelatin. The form of the pellet is almost unchanged. No flattening or expansion. The pellet did not tumble or deviate in the block. The AA field is my go to pellet for accuracy and will still put meat on the table with a well placed shot but it is not ideal when compared to hunting specific options.
Immediately we can see a huge difference. Penetration depth has halved and the width of the wound cavity has more than doubled. This demonstrates an ideal transfer of kinetic energy to the target. The wound cavity would prove catastrophic even if a shot were slightly misplaced and the pellet is likely to remain in the target.
We can see why the Terminator produced such a wide cavity and a shorter penetration. The pellet has changed shape dramatically. The front end has peeled backward and become wider. The Terminator was the fastest pellet on test at 764.4 which no doubt played a major part in the extensive deformation. For those of you who select pellets based on ft.lbs energy (a calculation of mass and velocity), you might be surprised to hear this pellet was 6th in terms of energy at target. It only produced 9.40ft.lbs compared to the 1st (Sniper Magnum) 10.53ft.lbs. Calculated energy doesn’t always equal large wound cavities… In my experience the energy is better delivered via the velocity part of the equation than the mass when it comes to forming large cavities in Gelatin.
The pellet has remained intact which is important for two reasons. If you are eating the meat then small bits of lead are an undesirable addition. Mass retention also ensures the pellet travels through the target causing a single deep wide cavity. A pellet which broke up rapidly would likely cause a very shallow penetration with multiple tiny wound tracks. That would increase the chance of your pest species being injured rather than a clean kill. Luckily the companies who manufacture premium pellets understand that and all pellets I tested retained their mass.
Another great performance from H&N. A nice wide cavity for the first 3″ and the pellet coming to a stop just beyond 4″. The pellet has maintained stability. The Hunter Extreme was calculated at 10.37ft.lbs (2nd to the Sniper Magnum) at target and was the second slowest pellet tested. Despite the lack of velocity due to its weight (9.57gns) H&N have done a great job on the design at the front end which still allows good deformation.
The front face of the pellet has visibly flattened and increased in diameter. The deformation is nice and even which ensures the pellet doesn’t yaw at all. I would be very confident in selecting these pellets for pest control.
The SHP Stopped at 3″ and produced a good cavity. Not quite as impressive as the Hunter Extreme but certainly not bad. At its widest point the cavity is more than wide enough to be really effective.
The Super H definitely has the most deformation of all pellets tested in this article. The front face has peeled right back past the bottom of the hollow point. This would be due to it being the lightest pellet tested (6.94gns) and the second fastest (744.7fps). The combination of less/thinner material and high speed produces more deformation. I am really surprised the wound cavity wasn’t more impressive and if we put some more shots in they possibly would be.
Now we are starting to see there are trade offs. If you sacrifice to much mass for velocity in a system where velocity is limited (either by law or mechanically) then the cavities will suffer because the overall energy is less. In this case the SHP’s had the least calculated energy at target (8.54ft.lbs).
A very interesting result from the Super Field. A good wound cavity out to 2.5″ and penetration out to just over 5″. If I had to pick one pellet from this test as a Jack of all trades it would be this one. Although the penetration is likely to cause the pellet to exit the target and waste energy there is no denying the cavity is more than adequate.
There is very little deformation to the pellet. The Pellet achieves a good balance of mass, and velocity which have produced a good result. We can now see that pellets which are not on the extreme ends of the velocity/mass scale could be a better choice in a non FAC rated rifle than something like the Sniper Magnum. If you are looking for a pellet that can be used for FT comps and knocking some rats over then this might be for you..
Another pleasant surprise from the non expanding pellets. The Exact produces a reasonable cavity up to 2″. After that the cavity tails off quickly and the pellet would likely leave the target due to over penetration. The Exacts produce the 3rd highest velocity on test and 3rd in terms of calculated energy at target (10.29ft.lbs). If it were able to expand/deform then it would produce a shorter, thicker cavity that would likely be superb.
Very little deformity on the front face. This would also be a pretty fair choice for those who want one pellet for everything. The JSBs are good value and I am impressed at the quality and consistency. It will be well worth testing these through an FAC rated Air Rifle to see if a velocity increase will aid expansion.
By far the heaviest pellet on test and the only slug type. The Sniper Magnums look more like a bullet than a pellet. I really had my doubts about this pellet in a non FAC rated gun. H&N do suggest a 12ft.lbs minimum so I don’t think this was very fair on it. However I did want to demonstrate that the heaviest pellets are not necessarily the “best” in all rifles. The increased mass and total lack of expansion meant this was both the smallest wound cavity and the biggest over penetration.
The Sniper Magnum had the highest calculated energy at target (10.53ft.lbs) which many hunters might be attracted by. It was also the slowest pellet on test (570.8fps). The lack of velocity and total lack of expansion mean the pellet is unable to transfer the energy to the target in a satisfactory manner. I would really love to test these in an FAC rated Air Rifle and see how they perform. On a side note these were the second most accurate pellet in my Ultra (Air Arms field were slightly better).
No great changes in shape. The Sniper Magnum is noticeably longer than any other pellet tested here. It also has the highest ballistic coefficient by quite a margin. Long low drag projectiles without expansion are really the worst case scenario in terms of wound cavity. If we could really increase the velocity and get a bit of expansion then I think the results would be good.
So what did we learn? Well we know that all systems we work with to transfer projectile energy to a target have limiting factors. The projectile can only be as large as the caliber/rifle allows. We also know that the velocity will be limited either by lower power (non FAC rated gun) or by physics.
Within these limits there is an ideal balance of weight, velocity and form factor which produce results deemed suitable for the chosen target. In the case of a non FAC rated Air Rifle it would appear the pellets with specific designs which magnify deformation are beneficial. They produced wider cavities are were likely to dump all their energy into the target without over penetrating. However that isn’t to say that FT type pellets do not produce satisfactory results. What we can say with certainty is that nobody should select a pellet as “the best for hunting” based on one variable (such as weight). Testing is required to establish which set of trade offs produce the result required.
If anyone would like to discuss this article further please feel free to email me at firstname.lastname@example.org. I will be testing more pellets in other calibers and hopefully in an FAC rated Air Rifle. Please let me know if you have any pellet testing requests for a specific brand/type and I will try to add them in.