Brass Fetcher Ballistic Testing
Airguns are terrific firearms for teaching new shooters to shoot, for pest control and just having fun. They replicate firearms in every way except for terminal ballistics—they are much less powerful than firearms. Airguns are still hazardous and I am aware of one confirmed human death after being shot with an airgun. When choosing a caliber, the two most popular choices are 0.177” bores and 0.22” bores. Other calibers such as 0.20”, 0.25” and 9mm were not widely available to the American market until recently. The larger the diameter of airgun pellet, the greater the penetration in soft tissue in most cases.
While powerful airguns are capable of killing small game I recommend that they be used for small rodents at a maximum.
There is simply not enough kinetic energy available in an airgun to allow for a humane shot on a larger animal.
Airguns use a variety of propellant types such as spring-piston, compressed air or CO2. In many countries it is legal to own sound suppressors and to use them on airguns. If a sound suppressor is legally available to you, there is no reason not to use one. The pre-charged gas guns are ideal for suppressed used since there is little to none of the mechanical noise associated with the spring-piston guns firing.
Selecting the proper ammunition for the target is very important with airguns since there is not much “butt” to go around with these weapons.
For small game, I see no reason to suggest the ‘hollowpoint’ pellets in 177– or 22-caliber. Five different brands were tested in the past and no expansion was observed at velocities less than 1100 ft/sec in ballistic gelatin or water. If you are looking for a reliable hollowpoint-type expansion at velocities down to approximately 450 ft/esc, simply turn a pellet around and shoot it backwards. This allows the thin walls of the skirt to expand. The expansion is very reliable but the accuracy and velocity retention at long ranges will suffer. As always: test your gun with different types of ammunition to see which works the best for your gun.
More precise shooting necessitates conventional ammunition loaded point-forward. There isn’t a lot of difference in terms of terminal performance between the different nose shapes. Through the use of slow motion video, we can observe the temporary cavity from the different nose shapes as they penetrate ballistic gelatin. While temporary cavity is not a wounding mechanism, it is a good qualitative indication of the wounding ability of the tested projectile.
Let’s take a look at the damage caused by the different pellet shapes:
The wadcutter is my pick for general purpose use. If driven over 800 ft/sec, the wadcutter will begin to expand in gelatin. When the velocity is less than 800 ft/sec, the disc profile maximizes fluid drag and subsequent tissue disruption. If the target is thin and pops up at close distance, you can turn wadcutters backwards and have a great hollowpoint bullet that expands in the target.
Following the lead of ammunition advances in tank ammunition, the Skenco ‘Hyper-Velocity’ pellet uses a plastic sabot and a 0.125” diameter penetrator rod as the projectile. My shooting impression with this ammunition in 0.177” caliber is that it offers good precision at 25 yards but accuracy becomes erratic if the round goes supersonic. It also causes my neighbors to call the police on me, so I always try to avoid sonic booms during backyard shooting events.
The sabot allows a light-for-caliber projectile to be used while the penetrator rod itself maintains a high length-to-diameter ratio. This ratio is critical for penetration and then tumbling inside of a fluid target. Below we can see this round function in gelatin overlaid on an anatomy chart for a full-size brown rat.
There are many different ammunition options available to the airgun shooter today. This webpage would not be complete if I did not mention the ‘other’ types of ammunition. If you need an extra 100-200 ft/sec velocity, it is possible to ‘diesel’ your airgun. Simply place petroleum-based household oil on the skirt area of your pellet, close the barrel and fire. This will increase chamber pressures inside of your gun and could damage your gun and the people near the gun. You will get a much faster shot but the difficulty is in doing this with consistency.
In order to evaluate the usefulness of the adult airgun in a last-ditch defensive situation, I took the most sectionally dense pellet commonly available (the Predator Big Boy), dieseled the shot and shot it into 10% ballistic gelatin. These results and many other 0.177” caliber airgun shots into ballistic gelatin are available in this report: (177 Caliber Airgun: Terminal Performance)
A higher performance option than the 177 caliber airgun is the 22 caliber airgun (see full report: 22 Caliber Airgun: Terminal Performance). This will naturally increase cost but there is really no other drawback. Additionally, the 22 caliber airgun will be able to inflict equal or greater damage and stay subsonic. Staying subsonic will reduce the odds that you will disturb those around you while shooting.