Maintenance · Explainer

How to quiet an air rifle (legally)

Researched by James · Updated September 26, 2026 · Editorial policy

Do factory-shrouded ("moderated") air rifles actually work?

Yes, noticeably. Many current PCP air rifles ship with the barrel enclosed inside a permanently built shroud, sometimes advertised as a "moderated barrel," installed by the manufacturer as part of the complete rifle rather than as a device the buyer attaches afterward. That housing quiets a real source of PCP noise: the rush of compressed air escaping around the pellet as it leaves the barrel, on top of the mechanical valve noise. Buying a rifle that already comes this way from the factory is the simplest way to get a meaningfully quieter gun without ever handling a standalone suppressor.

Power and pellet choice: staying below the crack

A pellet or slug that exceeds the speed of sound, roughly 1,100-1,125 fps depending on temperature and altitude, produces a sharp crack as it breaks the sound barrier, on top of whatever noise the rifle itself makes. Two separate choices keep you under that threshold:

• Pick a heavier pellet or slug. For a given power level, more mass means lower velocity, which is one reason heavier hunting pellets and slugs often run subsonic where a very light alloy pellet at the same energy would not.
• Use the rifle's own power adjustment. Many PCPs have a factory power wheel or similar adjustment that lowers velocity within a documented range. Dialing power down, within that range, is a legitimate way to trade some energy for a quieter, subsonic shot. See PCP regulators and power adjustment explained for how that adjustment actually works, and never push it past what the manufacturer specifies.

Neither of these is a substitute for adequate energy on game; a subsonic setup still needs to clear your quarry's energy floor at the ranges you actually hunt. See the FPE chart before trading power for quiet on a hunting rifle.

Backstops: the noise you're actually making at impact

A pellet striking a hard surface, a fence, siding, a wood post, makes its own sharp noise independent of anything the rifle does. A dense, absorbent backstop, whether that's a purpose-built pellet trap or a thick dirt berm, muffles that impact sound considerably compared to a hard surface. This matters as much for safety as for noise: a proper backstop is also what stops a missed or passed-through shot from going somewhere it shouldn't, which is non-negotiable for backyard or close-quarters shooting regardless of how quiet the rifle itself is. It's the same backstop discipline covered in how to teach someone to shoot an air rifle.

Is an airgun moderator legal? The federal definition

Federal law defines a "firearm silencer or firearm muffler" as "any device for silencing, muffling, or diminishing the report of a portable firearm" (18 U.S.C. § 921(a)(25)), and separately defines a "firearm" as a weapon that expels a projectile "by the action of an explosive" (18 U.S.C. § 921(a)(3)). Airguns run on compressed air or CO2, not an explosive, so they fall outside the federal "firearm" definition, and Airgun Depot's summary of the law notes airguns are "normally unregulated under the Federal firearms laws" as a result. That's the reasoning behind airgun-specific shrouds existing as a distinct product category from firearm suppressors. It is not a blanket guarantee that every device marketed for airguns is treated the same way in every jurisdiction, and it says nothing about state or local law, which is a separate question entirely.

Do state or local laws restrict airgun moderators?

Often, yes, and independently of anything happening at the federal level. Airgun Depot's overview points out that New York City, Washington D.C., large parts of New Jersey, and Philadelphia already restrict or ban airguns generally, and Illinois treats higher-powered air rifles as firearms outright, requiring the same credentials a gun purchase would. States that broadly restrict firearm suppressors don't always carve out an explicit exception for airgun-only devices, and definitions of "silencer" in state statutes don't always track the federal explosive-based "firearm" definition the same way. The only reliable answer is to check your own state's and city's current statutes, not to assume federal treatment settles the question locally.

What this page doesn't cover, and why

This page doesn't explain how to build, modify, or attach a moderator or suppressor to any gun, airgun or firearm. That's a deliberate scope limit, not an oversight: devices that reduce a gun's report sit inside a regulated category federally and in many states, the manufacturing and unlicensed distribution of which carries real legal risk, and getting it wrong isn't the kind of mistake you get to walk back. If quiet operation matters to your setup, a complete, factory-shrouded rifle and a subsonic pellet load get you most of the practical benefit without any of that risk.

For the accuracy side of a quieter, lower-power setup, see why is my air rifle inaccurate?, and for how factory power adjustment interacts with a regulator, see PCP regulators and power adjustment explained.

FAQ

Sources

• Cornell Law School, Legal Information Institute — 18 U.S.C. § 921(a): definitions (firearm; firearm silencer or firearm muffler)
• Airgun Depot — Are airguns considered firearms?
• NASA Glenn Research Center — Speed of sound
• American Airgunner — The beginner's guide to tuning a regulated PCP airgun