Suppressor Performance in Perspective
While working on compiling data for the Suppressor Performance Database, a surprising revelation came to me: suppressor comparisons, even between direct competitors, are not “apples to apples” endeavors. Indeed, two apparently similar suppressors may offer completely different shooting experiences. This has led me to wonder if the community has a whole has become so obsessed with decibel-chasing, especially as measured at the muzzle, that we often miss other important details that are equally relevant to the complete performance picture.
During my research, a lengthy thread at AR15.com sprung up where a shooter expressed some dissatisfaction with the SilencerCo Octane 45. After having a chance to shoot his Octane next to AAC’s Ti-Rant 45, he felt that his suppressor was significantly bested by the AAC can. His experience suggested that the Ti-Rant was noticeably quieter from the shooter’s perspective than the Octane when fired on the same gun using the same ammunition. Shooters who only passively dig into the issue might assume something was wrong with the Octane as it typically meters within a decibel of the Ti-Rant. Such a difference is hardly enough to pick a “winner.” If this is the case, how is it possible that the Ti-Rant could sound considerably better to most shooters? The answer lies in how each suppressor manages the hot gasses that have been “caught” by the baffles and which subsequently attempt to escape out of the back of the suppressor. This phenomenon is generally referred to as backpressure, and its severity is dependent on a number of factors, including baffle design and suppressor bore size.
Backpressure is something that suppressed shooters address and contend with regularly. This is especially true on rifle platforms where firearm design and human anatomy dictate that the shooter’s face must be held close to the rifle’s action. As far as suppressed rifles are concerned, backpressure is usually referred to in the context of comfort (gas blowback to the face) and cyclic rate. Because rifles are loud by their very nature, we often do not delve into backpressure’s effects on perceived or measured suppression. Typically, the discussion only goes deep enough to say that some suppressors are “gassier” than others, but at-ear SPL (sound pressure level) is largely ignored.
For our Octane/Ti-Rant discussion, backpressure remains a very significant factor and one that is usually not considered at all when suppressing handguns. When fired dry, many pistol shooters are unlikely to notice that one suppressor is “gassier” than another. The handgun is often just too far away from the user’s face to feel the gas blowback, and the pistol cartridge by its nature generates less pressure than a rifle round. Even so, the effects of backpressure and differences in suppressor design can be felt and measured with both handguns and rifles.
Without “at ear” SPL measurements, it is almost impossible for prospective buyers to determine which suppressor will sound better or provide a better experience to the shooter. The very nature of legal suppressor ownership makes even subjective analysis difficult to find for multiple suppressors. Unfortunately, objective testing data for at ear SPL is something that historically has been ignored in manufacturers’ publications and largely unavailable for the average consumer. Thankfully, Silencer Shop now includes such measurements as part of their frequent testing videos, and the results are enlightening, to say the least.
Because more data is currently available for the Octane 9 and Ti-Rant 9 suppressors (rather than the .45 ACP versions initially discussed), let us dive into the information Silencer Shop has gathered for these cans. A quick look at the spreadsheet shows that SPL attenuation, as measured near the muzzle, is virtually the same for each suppressor when used on the same host. Historically, this would be the only data available, and many shooters would consider the suppressors equals for all practical purposes. Moving to the at ear measurements, we begin to see the whole picture. Here, in extreme cases, the Ti-Rant comes out almost 3 decibels quieter than the Octane. While this is not a huge margin, it should be enough for shooters to detect a small advantage for the AAC can when used on the same host and in the same environment.
Interestingly, the Octane and Ti-Rant use two distinctly popular and competing baffle designs. The Octane’s famous click-together CTA baffles are conical in shape and made entirely of stainless steel. These cone baffles are popular for their simplicity and excellent performance. Compared to rival designs, cones take up less space in the suppressor tube and are usually rated for higher pressure levels, but their funnel-like shape does not effectively prevent gas from traveling back toward the shooter.
In contrast, the Ti-Rant uses a type of K-baffle. The Ti-Rant’s blast baffle is steel, but subsequent baffles are aluminum. The reason for this material choice is that a K-baffle is considerably more voluminous than a comparable cone baffle, and weight is a major concern, especially for pistol suppressors. When viewed from the side, the Ti-Rant baffles are shaped like a “K” with a flatter, ported blast surface that funnels gas along a cone-shaped secondary surface towards outer chambers at the suppressor tube’s walls. The relatively flat blast surface not only disrupts gas heading toward the muzzle, but it also traps hot gasses that attempt to travel backward, thus limiting backpressure. This design factor is largely why the Ti-Rant and Octane produce noticeably different results at the shooter’s ear but perform similarly at the muzzle.
A separate (but no less significant) consideration must be made when firing sub-calibers through larger suppressors on both rifle and handgun hosts. The “seal” between bullet and baffle that is achieved by firing the designated caliber through a suppressor minimizes gas escape and maximizes suppression at the muzzle, but also generates backpressure that ultimately releases in the direction of the shooter. A smaller diameter bullet will allow more gas to escape around the projectile and out the end of the can, but less gas will be directed back toward the shooter. This, in conjunction with increased suppressor length/volume, is largely why an Octane 45 can be expected to outperform an Octane 9 from the shooter’s perspective when used with 9mm ammunition. The same principle applies to AAC’s Ti-Rant series. While the .45 ACP suppressors are measurably less efficient at the muzzle, the 9mm cans relinquish their advantage (and then some) when we move back to the shooter’s viewpoint.
When talking about rifle suppressors, we see a similar trend. Measuring 1 meter left of the muzzle on a 16-inch AR-15, Silencer Shop has metered the AAC SR7 at 146.4 decibels. Under the same conditions, the AAC M4-2000 metered at 135.2 decibels. There is no question that 11.2 decibels is a huge difference, but what does this mean for the shooter? During the same test, the SR7 yielded an at ear average of 142.2 decibels compared to the 144.0 average for the M4-2000. The SR7 is just 1 inch longer and 2 ounces heavier than the M4-2000. Despite the impressive 11+ decibel disadvantage at/near the muzzle, the SR7 might actually sound better to some shooters and is almost guaranteed to produce less backpressure.
So why is this information significant? The answer to such a question can be found in a variety of places. First, muzzle (or near muzzle) testing for SPL attenuation seldom tells the whole story or even comes close to portraying the actual shooting experience with a particular suppressor. Suppressors that perform well at the muzzle frequently suffer when metered from the shooter’s perspective and vice versa. This is often attributable to bore size and baffle design. Second, the overall length can compensate for a larger bore aperture when it comes to muzzle readings, but it typically will not affect at ear performance. Lastly, reasonably over-bored (e.g., 9mm ammunition through a .45 ACP suppressor, 5.56mm through a 7.62mm can) suppressors will often produce a more pleasing result in terms of sound/tone and backpressure for shooters. Thus, shooters looking to save money by purchasing a single, larger bore suppressor are unlikely to feel shorted as far as practical suppression is concerned.
I thank Silencer Shop for adding these “at ear” readings to their tests as the data has proven to be immensely useful in effective suppressor comparisons. I hope readers, especially suppressor novices, will find this information enlightening and thought-provoking as they make their way through the often confusing world of “cans.”
An information security professional by day and gun blogger by night, Nathan started his firearms journey at 16 years old as a collector of C&R rifles. These days, you’re likely to find him shooting something a bit more modern – and usually equipped with a suppressor – but his passion for firearms with military heritage has never waned. Over the last five years, Nathan has written about a variety of firearms topics, including Second Amendment politics and gun and gear reviews. When he isn’t shooting or writing, Nathan nerds out over computers, 3D printing, and Star Wars.