Subsonic vs Supersonic Ammunition (What's The Difference?)

Basics of Subsonic vs Supersonic Ammunition

The video opens with Matt and Kyle introducing the topic of supersonic versus subsonic ammunition and noting that it’s surprising they haven’t covered it before. They immediately define the terms: a supersonic round travels faster than the speed of sound, while a subsonic round stays below that speed. They give the speed of sound as roughly 1,100 feet per second and explain that most common ammunition is naturally above that threshold, so it is typically supersonic. They point out exceptions, such as .45 ACP, where standard-pressure loads are usually around 850 feet per second, making them subsonic unless specifically loaded hotter. In contrast, 5.56 is described as a cartridge that relies heavily on high velocity for performance, so it is almost always loaded to be supersonic, even though it can technically be made to run slower. They emphasize that many calibers offer both super and subsonic options, setting the stage for why a shooter might choose one type over the other.

Noise Components, Suppressors, and Subsonic Advantages

Matt and Kyle move into why someone would choose subsonic ammunition, focusing on noise reduction, especially when using a suppressor. They break down three main contributors to the sound of a gunshot: the mechanical action of the firearm cycling, the rapid depressurization of gases as they exit the muzzle behind the bullet, and the sharp crack created when a projectile breaks the sound barrier. A suppressor primarily addresses the gas blast at the muzzle, while subsonic ammunition removes the downrange crack by never exceeding the speed of sound. That leaves mostly mechanical noise, which is even less noticeable in a manually operated bolt-action rifle. They explain that subsonic loads are generally slower and therefore have more bullet drop and less energy at distance, but manufacturers often use heavier bullets and reduced powder charges to keep velocity down while still maintaining useful impact performance. They also highlight that barrel length matters: a 9mm load designed to be subsonic in a handgun can pick up enough speed in a longer carbine barrel to become supersonic, changing its behavior and sound.

7.62x39 Test with Meridian Defense Vulk and SureFire Suppressor

At the range, the first live-fire example uses a Meridian Defense Vulk rifle chambered in 7.62x39 with a SureFire suppressor. The shooter loads a magazine with five supersonic rounds followed by five subsonic rounds to allow a direct comparison. When the supersonic ammunition is fired through the suppressor, the overall report is noticeably reduced compared to an unsuppressed rifle, but the distinct crack of the bullet traveling faster than sound is still clearly audible. When they transition to the subsonic 7.62x39 rounds, the character of the sound changes dramatically. The report becomes much softer and more muted, closer to what many people imagine when they think of a suppressed rifle in movies. They briefly confirm that the rifle still cycles reliably with the subsonic loads and point out how the combination of a suppressor and slower ammunition significantly alters the perceived sound signature while keeping the gun functional.

MP5 9mm Suppressed with Supersonic and Subsonic Loads

Next, they move to a 9mm MP5 equipped with a suppressor and a UTG Ultra rail that is mentioned as an upcoming accessory. The magazine is loaded with ten supersonic 9mm rounds followed by ten subsonic rounds. When the shooter begins firing, the suppressed supersonic ammunition already sounds relatively quiet, to the point that there is a moment of uncertainty about when the switch to subsonic occurs. As the subsonic rounds are fired, the difference becomes more apparent: the overall sound level drops further and the sharp, high-pitched crack disappears, leaving a softer, more thudding report. Matt and Kyle comment that both loads are comfortable to shoot through the suppressor, but the subsonic ammunition clearly produces a gentler, more subdued sound, illustrating how pistol-caliber carbines can benefit from pairing slower loads with a quality suppressor.

.22 LR Glock 44 with Supersonic and Colibri-Type Rounds

The demonstration then shifts to a Glock 44 pistol chambered in .22 LR, this time fired without a suppressor to show what very low-velocity ammunition can do on its own. The magazine is loaded with five standard .22 LR rounds that are typically supersonic and five very low-power Colibri-style rounds that rely mostly on primer compound with minimal or no traditional powder charge. Firing into the berm for a direct sound comparison, the standard .22 LR rounds produce the familiar small-caliber crack. When the Colibri-type rounds are fired, the report is dramatically quieter, almost like a loud air gun. Because these ultra-low-velocity rounds generate so little energy, the slide does not cycle on its own and the pistol must be manually worked after each shot. The hosts describe the recoil as extremely soft and note that this kind of setup can be useful for training new or younger shooters who might be sensitive to noise and recoil, while also demonstrating how much sound can be reduced simply by lowering velocity, even without a suppressor.

.300 Blackout Christensen Arms Ridgeline Scout Bolt Gun Demo

For the final live-fire example, they use a Christensen Arms Ridgeline Scout bolt-action rifle chambered in .300 Blackout and fitted with a suppressor. The magazine is loaded with several supersonic rounds followed by subsonic .300 Blackout. Because the rifle is a bolt gun, there is very little mechanical cycling noise, so the primary sounds are the muzzle report and the bullet impact. When the supersonic rounds are fired into the berm, the shots are already relatively quiet through the suppressor, but there is still a noticeable crack and a brisker report. Switching to subsonic .300 Blackout, the sound becomes extremely subdued, with the thud of the bullet hitting the dirt backstop sounding louder than the shot itself. Shooting at a 100-yard berm, they point out the slight delay between the muted muzzle blast and the audible impact, which underscores the slower travel speed of the subsonic load. This sequence reinforces why .300 Blackout is so closely associated with suppressed, slower-velocity use in bolt guns and other platforms designed around quiet performance.

Key Takeaways on Subsonic vs Supersonic Use

To wrap up, Matt and Kyle summarize the main lessons from the range demonstrations. Suppressors provide a meaningful reduction in noise even with supersonic ammunition, but the quietest and most dramatic change in sound comes from combining a suppressor with subsonic loads. Subsonic ammunition is typically built with heavier bullets and reduced powder charges to stay under the speed of sound, which trades some trajectory flatness and impact energy for a much softer report. They stress that barrel length can change how a given load behaves, potentially pushing a round that is slow in a handgun into faster territory in a longer barrel. The different platforms they used—the Meridian Defense Vulk in 7.62x39, the MP5 in 9mm, the Glock 44 in .22 LR with Colibri-style rounds, and the Christensen Arms Ridgeline Scout in .300 Blackout—each highlight how speed, barrel length, and suppressor use interact. They encourage viewers to think about their specific goals, whether that is maximum effectiveness, reduced noise, or a balance of both, when choosing between super and subsonic ammunition.