Mike Morton heads to the kitchen and cooks up a batch of ballistic gel to find out how much pellet shape and calibre matter when it comes to a clean kill.
An ethical hunter has one thing in mind when they take a shot: the need to ensure a swift, humane kill. A couple of factors come into play here, the first being shot placement. A hunter has to know exactly where they want that shot to land – and have the skill, experience and equipment to reliably deliver it.
Then there’s the effect of the pellet on the quarry animal. It has to cause massive trauma to the target area, usually the brain, but sometimes the heart and lungs, depending on the specific animal that’s being targeted and the way the shot is presented.
This is terminal ballistics: how the pellet behaves and the way in which it transfers kinetic energy when it makes contact with the target. A quarry animal will die if the pellet has severely interrupted or stopped the flow of oxygenated blood to the brain by damaging a major blood-carrying organ such as the heart and lungs, or by severely damaging the brain itself.
The amount of damage done to these areas is a function of the pellet’s terminal velocity, and potentially
its design and length as well.
A projectile hitting soft tissue and bone will create two types of wounds called cavities, these being either primary or temporary. The primary cavity, which is also known as a permanent cavity, is the wound channel made by the projectile itself, and will be the same size as the initial hole made by that projectile – in our case that means the calibre of the pellet.
But when a pellet strikes our quarry it will also cause a temporary cavity. As the pellet hits the animal, the soft tissue will initially stretch as it tries to absorb the energy of the shot.
This tissue will keep stretching until it finally gives way, being violently cut and torn as the pellet travels through it before eventually returning to its normal, albeit damaged, position.
This sounds quite horrific, and it is. But in terms of hunting, this is highly desirable for both the hunter and the animal, because cavitation that causes maximum damage to a vital area means an instantaneous and painless death. What’s therefore required is to place that pellet so it will maximise cavitation around the brain or heart and lung areas, again depending on quarry species.
With powder-burners, a bullet’s design plays a huge role in how this energy is transferred. If a bullet expands when it hits soft tissue, it will increase cavitation, but it won’t penetrate as far through the tissue. Conversely, a deep-penetrating bullet won’t cause as much cavitation.
This is important for the powder-burner hunter who will need to use a completely different type of bullet to kill a fox as they would to shoot a large animal such as a red deer.
But what about the airgun hunter?
We’re dealing with small, light animals such as rabbits, pigeons and squirrels. I wanted to find out whether any of the various pellet designs transfer energy better than the others, and whether calibre choice really does make a difference. So it was time to get shooting into some ballistic gel.
Ballistic gel is a testing medium that is designed to replicate muscle tissue so that the effects of a projectile can be determined. It was initially developed by the US Army in the 1950s to test full metal jacket bullets against simulated human flesh, but is extremely useful for testing hunting rounds too – and that includes pellets.
Ballistic gel is now widely used by both NATO and the FBI, with NATO-grade gel being more dense as it has to cope with deeper-penetrating FMJs rather than hollowpoints. When dealing with human targets, it’s also possible to pour the gel into chest or head-shaped moulds that include a rigid material that simulates bone.
That’s a bit over the top for the airgun shooter, so I wanted to use some basic FBI-grade ballistic gel. After all, we’re looking at putting squirrels in our sights, not insurgents. The gel I used here represents animal muscle tissue.
It doesn’t take into account bone, feather or fur, any more than FBI gel takes into account a suspect’s clothing, but nevertheless provides an interesting insight into what happens when a pellet strikes and penetrates a quarry animal.
Ballistic gel can be bought fairly easily in the US, but is not so straightforward to find in the UK, presumably because there’s such a limited market for it. I had to make my own, so it was time to get into Breaking Bad mode and play Heisenberg. I had never made ballistic gel before, but had always enjoyed watching YouTube videos of it being made and tested (thank you MythBusters).
However, it soon became clear that not all homemade ballistic gels are created equal. The gel I’ve made here, which is basically just animal gelatine and water, seems to be the best of the bunch, and until the FBI contacts me to say I’ve got it wrong, this is what I’ll continue to go with. It’s pretty easy to make, fairly cheap, and the gel can be reused.
At its heart, ballistic gel is a stabiliser derived from animal collagen. It’s the ratio of gel to water that’s important. For use in the kitchen, it can be bought in sheets or powdered form, but powdered gelatine dissolves more readily, and so that was what I used here.
Powdered gel can be bought in supermarkets, but it’s usually sold in very small packets and is therefore uneconomical to buy this way for our needs. My gelatine powder was purchased online from a firm called ClassiKool. One 500g packet is enough to make 4.5 litres of ballistic gel. This particular gel powder is made from pig skin, and despite the fact that I’m a confirmed hunter and meat-eater, I found the smell quite revolting. If your partner’s a vegetarian, make sure they’re nowhere near the kitchen…
The powder needs to be dissolved in hot water. This can be done using nothing more than hot tap water, but I chose to make mine in a cooking pot on the hob as it gave me more control and working time. The only other ingredient you may need is a small bottle of cinnamon leaf oil, which for me was another online purchase.
If you stir in the gelatine too vigorously, it can form bubbles which will ruin the consistency of your gel.
A few drops of oil will dissipate those bubbles. As an added benefit, it will also make the gel smell quite pleasant, eliminating its original porcine odour. If you stir slowly by hand, taking care not to create too many bubbles, you may get away without the need for any oil altogether.
Ballistic gel, even when properly set, needs to be stored at around five degrees Celsius (41 degrees Fahrenheit) for it to maintain the correct density to replicate animal tissue. This means you’ll need to keep it in the fridge and transport it to the range in a chiller if it’s to work properly.
The good news is the fact that after it’s been shot, the pellets can be dug out and the gelatine block melted down and remoulded for future use. Gelatine contains no preservative, however, so it will eventually go mouldy and should be discarded after a couple of weeks or so.
It was time to get shooting. I used my Weihrauch HW 100 in .177 and my BSA R-10 SE in .22, as apart from being fantastic rifles in their own right, both have a muzzle energy of 11.3 foot pounds with their preferred pellets, so the results would be based on as level a playing field as possible.
Shots were taken at a range of 30 yards, with two shots being taken at each block.
A further block of gel was shot at 10 yards with domehead pellets only – you’ll see why later. Before we begin, you may be asking yourself if this is a complete waste of time if you don’t hunt. Well possibly, but my advice is to try it anyway – it’s great fun and was quite enlightening!
Super Field .177 vs Super Field .22 at 30 yards
I chose to start the test with classic domehead pellets. Conventional wisdom told me that the .177 pellet, which is supposedly prone to over-penetration due to its smaller frontal area and more concentrated energy, would penetrate further. Conventional wisdom got it wrong.
The .177 pellet penetrated 10.5cm into the ballistic gel before coming to a standstill, while the .22 variant of the same pellet managed to travel 14cm. The .177 projectile caused only the primary cavity, while the .22 created a temporary cavity from 3cm to 8.5cm through its total 14cm of travel. Neither pellet deformed.
Superpoint Extra .177 vs Superpoint Extra .22 at
30 yards
Next up were the pointed pellets, which are designed to pierce through fur, feather and bone. The .177 Superpoint penetrated 12.5cm into the gel, while its .22 big brother went 14.5cm. Both pellets created a small amount of temporary cavitation almost immediately after hitting the gel. Neither pellet deformed.
Supermag .177 vs Super-H-Point .22 at 30 yards
Now it was the turn of the flatheads and hollowpoints, which are designed to quickly dump their energy into the target, causing greater shock damage. These two pellets differ from each other however, with the Supermag having a flat head like a target-orientated wadcutter, while the Super-H-Point has a proper hollowed-out head. While these two aren’t exactly a 100 per cent comparison, they do come from RWS’s Field Line and are both intended
for hunting live quarry.
So how did they fare? The Supermag .177 travelled 11.5cm into the gel, while the Super-H-Point penetrated slightly further to end up 12.5cm from the entry point. Neither pellet displayed any temporary cavitation and neither pellet deformed.
Super Field .177 vs Super Field .22 at 10 yards
I decided to carry out one more test, this time at close-range and using regular domeheads again to see what difference,
if any, there would be when these pellets were shot at 10 yards, thus retaining more energy than back at 30. The Super Field .177 travelled 12.75cm into the gel, while
its .22 counterpart went 14.5cm. The .177 pellet displayed a fair amount of temporary cavitation from 3cm to 6cm into the gel, while the .22 displayed only primary cavitation. Neither pellet deformed.
CONCLUSION
These results were certainly interesting, and not at all what I’d expected. In every case, the .22 pellet travelled further than its .177 counterpart. Temporary cavitation, except
at very close range, was either minimal or non-existent, and no pellet deformed at any range.
But all these different ammo types brought home the sheer amount of energy that a pellet can carry into a target from a sub-12ft-lb rifle. It’s worth remembering that this particular gel, at this density and temperature, represents muscle tissue. While a typical .308 rifle has a massive muzzle energy of 2,700ft-lb, take a look again at what those 11.3ft-lb rifles achieved here. It’s quite a sobering thought.
Ultimately, this test has highlighted one very important thing – the need to pick a calibre you are happy with, pick a pellet
that both you and your rifle like, learn its trajectory and place those pellets accurately. That’s what will truly help to guarantee a clean kill, which is better for you and better for your quarry.
More from our experts on airgun pellets
- Best pellets: how to choose the right one
- What is the best calibre for hunting? Find out by clicking here
- RWS Super Field: Pellet test
- Pellet test: Webley Mosquito Express
- Pellet Test: Power-Force Field
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