Today at the range, something unexpected happened, and it had me doing a double-take with a grin on my face. Armed with my FX Dynamic .35 cal and my trusty DonnyFL Yokozuna airgun suppressor, I was ready for a quiet, relaxing shooting session. But what I got was… CRACK! Wait, what?! CRACK-CRACK! Was my suppressor broken? Nope—just good ol’ supersonic science in action. Let’s kick things off with a fun reality check about airgun suppressors and why trying to suppress the supersonic crack is a fool’s errand.
The Myth of Suppressing Supersonic Crack
Here’s the deal—an airgun suppressor (or any suppressor) can only do so much. It tames the muzzle blast by capturing and slowing the expanding air behind your projectile, but it can’t do anything about the supersonic crack happening downrange. That sharp boom comes from the projectile breaking the sound barrier after it’s already left the barrel. Unlike the muzzle blast, which is contained and redirected by the suppressor, the sonic boom is a result of the projectile creating shockwaves in open air. So, if you’re hearing that crack, it’s not your suppressor’s fault—your slugs are simply moving faster than sound itself. – pun fully intended – at the range with my FX Dynamic .35 cal shooting 68-grain FX Hybrid slugs, and it’s left me grinning like a kid on Christmas morning. Let’s talk about one of my favorite parts of airgunning: ballistics science, specifically how temperature affects the transonic region of a projectile’s flight. Buckle up, because we’re diving deep into air density, sound barriers, and the supersonic crack you chase (or avoid) when shooting.
The Science of the Transonic Region
First, let’s break down what happens when a projectile transitions from subsonic to supersonic speed. The transonic region sits in a range around the speed of sound. Depending on conditions, this range is generally between 0.8 and 1.2 times the speed of sound. As a projectile passes through this turbulent zone, air resistance and shockwaves wreak havoc on stability. Keeping your projectile within the right velocity range for precision shooting is key—too fast, and you flirt with chaos; too slow, and you lose energy and range.
It’s important to note that airgun projectiles are slowing down the moment they leave the muzzle. Unlike a jet plane accelerating through the sound barrier, a pellet or slug fired from an airgun enters the transonic region on its way back down through the speed of sound. That sharp supersonic crack you hear is caused by the projectile decelerating through the barrier, not accelerating into it. Many new shooters miss this distinction when studying ballistic models, often forgetting that when reading drag models, you should be interpreting them right to left (as velocity decreases), not left to right (as if the projectile is accelerating). The crack you hear isn’t from speeding up but from slowing down through the transonic spike. If your projectile is going to go supersonic, it will do so right at the muzzle, not downrange—so read those graphs right to left.
The speed of sound isn’t a fixed number—it depends on air density and temperature. As temperature drops, the speed of sound also decreases. This is the crux of what made today’s experience so enlightening.
RMAC and Chasing the Supersonic Dragon in the Desert
Let’s rewind to last year’s Rocky Mountain Airgun Challenge (RMAC) in Utah. The summer heat was cranked up to 90 degrees, and I was running my FX Dynamic .35 cal with 68-grain FX Hybrid slugs, trying to push them into supersonic territory. My goal? Hear that signature supersonic crack that tells you, "Ohhhhh ya!" you've broken the sound barrier. I was sending them downrange at 1080 feet per second (fps), gritting my teeth with excitement… but it never came.
Why didn’t I get the sonic boom? At 90 degrees, the speed of sound hovers around 1150 fps. Despite my best efforts, I simply couldn’t push those slugs fast enough to breach that barrier. The summer heat made the atmosphere less dense, requiring higher velocities to go supersonic. It was frustrating but fascinating, a real-world demonstration of how temperature plays with the speed of sound.
Back in Northern Michigan… With a Surprise
Fast forward to today’s range trip. It’s a crisp, finger-numbing 24 degrees here in Northern Michigan—a far cry from Utah’s sweltering heat. Armed with my FX Dynamic .35 cal and the same 68-grain FX Hybrid slugs, I wasn’t even thinking about the sound barrier. I was there to enjoy some good ol’ trigger time and fine-tune my setup using the FX True Ballistics Chronograph.
And then… CRACK!
Wait, what?! CRACK-CRACK-CRACK! Shot after shot, my slugs tore through the sound barrier, producing that sweet, unmistakable sonic boom. My chronograph confirmed the same muzzle velocities I had seen in Utah—around 1075 to 1080 fps—but the result was completely different. So what changed? The air. The temperature. The science.
Temperature and the Speed of Sound
At 24 degrees Fahrenheit, the speed of sound drops to roughly 1075 fps. Compare this to Utah’s 90-degree speed of sound at around 1150 fps, and you’ll see the massive shift. The colder air is denser, and denser air transmits sound waves more slowly, meaning the sound barrier exists at a lower velocity.
Here’s a basic breakdown of how temperature affects the speed of sound:
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At 32°F (0°C), the speed of sound is approximately 1,088 fps.
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At 68°F (20°C), it increases to about 1,126 fps.
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At 90°F (32°C), the speed of sound rises to around 1,150 fps.
Temperature directly affects air molecules' energy and spacing, altering the speed at which sound waves travel. This shift matters in airgunning because when you push projectiles to the edge of the transonic region, the threshold changes with temperature. What worked for precision shooting in summer might bite you in the winter unless you account for these shifts.
Hypothesis: Temperature and Precision Shooting
Precision airgunners know that shooting too close to the sound barrier invites turbulence, drag, and a loss of stability. The golden rule? Stay about 100 fps below the speed of sound for the most consistent results. This is why almost all precision .22LR firearm ammunition is loaded to velocities in the 1040 to 1070 fps range—balancing stability and precision by avoiding the turbulence of the transonic zone. But here’s the twist—if the sound barrier drops in cold weather, so does the target velocity for precision.
Consider this:
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In Utah’s 90-degree heat, aiming for 1050 fps kept you about 100 fps shy of the 1150 fps sound barrier.
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In Michigan’s 24-degree chill, that same 1050 fps now pushes you right into the transonic zone, where the sound barrier is only 1075 fps.
To avoid turbulence, you’d need to adjust your winter shooting speeds down to about 975 fps—a full 75 fps lower than your summer setup. That’s a big shift, and one that could make or break your accuracy if overlooked.
Shooting Supersonic: Fun, but Not the Goal
Let’s get something straight—chasing supersonic speeds isn’t usually a goal in airgunning. It’s a fun demonstration of what your airgun can do, especially when you’re running a powerhouse like the FX Dynamic. But it’s not something you should strive for when precision is the name of the game. The turbulence, drag, and shockwaves that come with transonic flight are accuracy killers.
When you hear that satisfying CRACK, it’s an auditory nod to science in action. However, it’s important to keep in mind that supersonic speeds introduce instability. For precision shooting, staying well below the sound barrier offers smoother trajectories and less disruption. With an airgun capable of serious power, like my FX Dynamic, it’s tempting to push the limits, but know your context: supersonic shooting is a novelty, not a benchmark for performance.
If anything, exploring the supersonic realm gives us a unique way to appreciate the science behind airgunning. Understanding the interplay of temperature, air density, and sound barriers teaches us how to fine-tune our setups for optimal results—whether we’re chasing cracks or tight groups.
Practical Takeaways for Airgun Ballistics
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Temperature Awareness Matters: Before heading to the range, check the temperature and adjust your expected transonic and supersonic thresholds accordingly.
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Chronograph Every Range Session: Don’t assume velocities from last summer will perform the same way in winter. Temperature changes everything.
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Target a Safe Margin: If 100 fps below the sound barrier is your golden rule in summer, apply the same buffer for winter by recalculating the speed of sound.
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Consider the Projectile’s Role: Heavier slugs might be more forgiving when pushing velocities, while lightweight pellets or slugs are more susceptible to transonic instability.
Closing Thoughts
Airgun ballistics is a playground of science and fun, where variables like temperature, pressure, and velocity dance in a delicate balance. Today’s range session was a vivid reminder that every shot is a lesson if you pay attention to the details. The next time you head out into the cold, remember—the speed of sound has slowed down, and your slugs will sing a different tune. Adjust, adapt, and always chase that perfect shot with a smile.
WOOOHOOOO! Science, baby!