Moderator Configuration & Optimization

If you're shopping for one of our moderators and aren't sure which variant fits your rifle, this page exists for you. Our designs work fundamentally differently from most moderators on the market, and that difference means selection actually matters. Picking the wrong variant for your application leaves real performance on the table. This guide gives you the tools to match our moderators to your specific rifle with confidence.

To do that, we need to share a bit of vocabulary. These terms come up throughout this page and across our product listings:

• Flow factor: Our shorthand for the volume and pressure of air a rifle serves to the moderator with each shot. It's a calculated value derived from your tank's pressure, volume, and shot count, and it's the single most important variable in selecting one of our moderators.

• Gas diode: The core technology behind our moderator designs. Invented by Nikola Tesla, a gas diode is a valveless fluid control device that allows fluid to flow freely in one direction while resisting flow in the other through geometry alone, no moving parts. We use compound gas diode stages to delay and redirect propellant air inside the moderator, which is a bit part of what separates our designs from conventional baffle-stack moderators.

• Damping: The sound-absorbing stage of our moderator design. Most moderators on the market focus on either flow control (baffle stacks) or sound absorption (damping material), and repeat that single approach the full length of the tube. Our designs do both, and adapt along their length, applying the right technique at the right point in the air's journey through the moderator.

• Saturation: The point at which a gas diode stage reaches optimal operating conditions for a given airflow. A diode tuned for high flow won't saturate correctly on a low-flow rifle, and vice versa.

• Peak: The maximum instantaneous sound pressure level recorded during a shot event.

• RMS: Root mean square, a measure of total sound energy over the full duration of a shot. This often matters more to the ear than peak alone.

Our moderators are tested on real rifles with real acoustic measurement equipment. What we know, we learned by building things, measuring them, and iterating. That process is ongoing, and we make no claim to having arrived at a final answer. Every design revision has been backed by data, and we publish that data because we think you deserve to see it.

Calculating Flow Factor

Flow factor is the most important variable in selecting one of our moderators, and this section gives you the tools to calculate it for your rifle. The formula, derived from the ideal gas law, is shown at right. It quantifies the air your rifle serves to the moderator with each shot, and the calculator below will do the math for you. Units matter: pressure in BAR, tank volume in cc.

There's one additional variable that's easy to overlook but has an outsized effect on the result: your shroud. This is where the shroud factor comes in. A shroud pre-expands propellant air before it reaches the moderator, and the difference between a well-shrouded rifle and a bare muzzle is dramatic enough that we built it directly into the formula.

Shroud factor guidelines:

• Efficient full-size shroud (e.g. FX Crown, 28mm OD): shroud factor of 1. This is the reference standard.

• Small or inefficient shroud (narrow diameter, or air preferentially directed into the moderator rather than pre-expanded): shroud factor of 1.2 to 3 depending on how restrictive. When in doubt, start at 1.5.

• No shroud, threading directly onto the barrel: shroud factor of 6. This is backed by testing, and yes, the difference is that significant.

• Shroud with internal baffles or unusually large volume: potentially below 1, though this requires further testing on a case-by-case basis.

Shroud quality also directly affects how loud your rifle will be regardless of which moderator you run. A poor shroud or no shroud means substantially more noise at the muzzle, full stop.

Our four reference hosts, which represent the tuning points for our moderator variants, are:

• Standard Flow: FX Crown .22 producing 32 foot pounds. Factory configuration w/ extended shroud acoustic peak is 288.0. Flow Factor 460.

• Moderate Flow: FX Crown .30 producing 80 foot pounds. Factory configuration w/ extended shroud acoustic peak is 637.6. Flow Factor 1,111.

• High Flow: FX Dreamline .30 producing 87 foot pounds. Bare muzzle configuration (un-moderated) acoustic peak is 3,668.4. Flow Factor 6,500.

• Extra High Flow: AEA Challenger .35 producing 150 foot pounds. Bare muzzle configuration (un-moderated) acoustic peak is 5,255. Flow Factor 16,333.

If you have a rifle significantly outside this performance range, you might want to get in touch before picking up a moderator as it may not be suitable for your application.

Simple spreadsheet calculator for flow factor

Peak, RMS, and Why Both Matter

While flow factor is superficially a question of what gun the moderator was tuned on, some of it comes down to an internal design ratio. Given space constraints, you're forced to split a design between elements which delay the flow of air and ones which absorb sound. The important difference is that the former acts to reduce peak sound signature while the latter primarily acts to clean up the noise produced after the peak.

Post-peak sound matters, and it's worth understanding why. The analogy that best explains it is a hammer striking a nail. A hammer blow is measurably an extremely loud event, but its brevity causes the ear to perceive it as not particularly loud. This is a known acoustic phenomenon, and has to do with a muscle reflex inside the ear. Were the sound of that hammer blow to be played continuously though, it would be physically debilitating. This is why traces are provided with every peak measurement: so you can get an idea of the total sound profile rather than just the nominal peak.

When it comes to higher airflow designs, a greater ratio of their internal space must be utilized to delay that air to keep it from rushing out the muzzle immediately. That means more post-peak noise. This is why you really don't want the higher flow variants unless you actually need them, as they will not outperform their standard flow counterparts in lower flow applications. Gas diodes are also tuned to saturate and perform best at specific flow levels, so putting a higher flow tuned diode in front of a lower flow rifle won't produce optimal sound attenuation regardless of peak numbers.

The two traces on this page illustrate this well, noting that they are NOT on the same Y-axis scale. Both produce roughly the same peak, yet the difference in perceived loudness is stark, and that comes almost entirely down to post-peak sound character.

Further Tricks for Sound Attenuation

Moderator Revisions & Development

Our moderators are built around a standardized anodized aluminum tube architecture. This wasn't purely an acoustic decision; it was a development one. Earlier designs used carbon fiber tubes, which were strong and light but monolithic. Once built, they couldn't be meaningfully modified. Testing a new core required building an entire new moderator from scratch, which slowed iteration considerably. The aluminum tube system changed that. Cores, diode sections, and damping sections can all be swapped independently, which means we can test a new idea without rebuilding everything around it. For users, this means end caps can be swapped to accommodate different muzzle threads, and cores can be upgraded as the technology advances without replacing the whole moderator.

It's also worth noting what doesn't change: the tubes themselves. The Falx is the Falx, the Sarissa is the Sarissa. We don't retire names and launch slightly reshuffled products under new branding every time we improve something. The external dimensions stay the same across revisions. What changes is everything inside, and over time that change has been substantial.

That stability is also what makes a formal revision system meaningful. Major version increments represent substantial performance jumps and introduce internal incompatibilities, meaning a rev.3 damping section won't drop into a rev.1 diode design. Minor version increments, say rev.2.0 to rev.2.1, are more surgical, and may allow individual components like a diode section or damping section to be swapped for the updated part. We're a research-focused company and expect this system to continue evolving. What's documented here reflects the current state of development.

The three major revisions to date:

• Rev.1: The original aluminum tube design. Diodes and damping were adapted and optimized from our earlier carbon moderator line, specifically the Levitas and Pilum series, and reengineered to work within the new standardized tube architecture. The damping section was fully floating, permitted by the modular design, and retention struts were thinned to improve sound penetrance into the damping material.

• Rev.2: Introduced a new diode geometry built around hollow, expanded struts. Rather than struts simply providing structural support, they were redesigned to also serve as flow channels feeding the diodes directly. This freed up internal volume, improved diode efficiency, and increased stopping power substantially. The tradeoff is that this diode requires more air to saturate and reach optimal function, which is why there is no standard flow rev.2 variant. The damping section saw incremental improvements throughout revisions 1 and 2 but no fundamental redesign.

• Rev.3: A ground-up overhaul of the damping system. Rev.3 combines the diode advances of previous versions into a more integrated structure while dramatically increasing the surface area of the closed damping material and more precisely tuning the flow resistivity and impedance of the open damping material. The result is meaningful improvement in both peak suppression and total A-weighted RMS noise reduction across all flow ranges. Rev.3 also brings improved durability, a practical necessity as big bore airguns have become increasingly common at the higher end of our supported flow factor range.

Sitting alongside the standard line is the Accipiter series. Accipiter moderators follow the same revision system and use the same fundamental diode and damping designs as their Falx and Sarissa counterparts. The difference is one of degree rather than kind. Every dimension, material, and geometry has been reanalyzed and pushed as far as it can go in the direction of reduced weight and improved acoustic performance. The analogy that fits best is running an engine past the redline: it's the same engine, just taken further, at greater cost. For users who need the absolute best performance-to-weight ratio available, that's what the Accipiter line represents.