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Reservoir Mods are 3 Legged Thing's airgun moderator range — British-designed and built specifically for air weapons. Available for .177 and .22 calibre airguns in multiple thread fittings including 1/2" UNF and 3/8" UNF, to suit a wide range of rifles and air pistols.

Lightweight, corrosion-resistant, and engineered for consistent performance and long service life. Suitable for target shooting, pest control and general field sports use.

Not ready to pre-order yet? Want to know more about how they work, and the engineering behind them? Scroll down for the technical bits!

THE SCIENCE OF SILENCE

CHAMBER SUPPRESSION ARCHITECTURE - ENGINEERING DIAGRAMS

  • Reservoir Mods 5-chamber diagram

    STAGE 01 - ENTRY & FIRST EXPANSION

    High-pressure gas enters immediately behind the projectile. The bore opens into a precision-calculated volume, triggered the first and largest pressure drop.

    STAGE 02-04 SEQUENTIAL VORTEX

    Air expands and vortexes within each successive chamber. Compressed wool gaskets strip residual energy between every stage - natural, dense, acoustically selected.

    STAGE 05 - FINAL ATTENUATION

    By the 5th chamber pressure is reduced to near-ambient.The exit report is a fraction of the original muzzle energy - clean and controlled.

    STAGE 06 - UNDISTURBED FLIGHT - BY DESIGN

    The projectile leaves the bore ahead of the propellant gas. By the time that gas is vortexing through the chambers, the pellet is already in free flight — completely clear of the turbulence. The Mod manages the report. It never touches the trajectory.

  • RESERVOIR MODS XL 8-CHAMBER DIAGRAM

    STAGE 01 - ENTRY & FIRST EXPANSION

    High-pressure gas enters immediately behind the projectile. The bore opens into a precision-calculated volume, triggered the first and largest pressure drop.

    STAGE 02-07 SEQUENTIAL VORTEX

    Air expands and vortexes within each successive chamber. Compressed wool gaskets strip residual energy between every stage - natural, dense, acoustically selected.

    STAGE 08 - FINAL ATTENUATION

    By the 8th chamber pressure is reduced to near-ambient.The exit report is a fraction of the original muzzle energy - clean and controlled.

    STAGE 09 - UNDISTURBED FLIGHT - BY DESIGN

    The projectile leaves the bore ahead of the propellant gas. By the time that gas is vortexing through the chambers, the pellet is already in free flight — completely clear of the turbulence. The Mod manages the report. It never touches the trajectory.

Chamber Absorption Technology

THE MATERIAL
THAT DOES THE
REAL WORK

Every chamber in the Reservoir Mod contains a precision-cut wool/polyester gasket disc. They are not packing material. They are not incidental. At 277 kg/m³ — nearly four times the density of high-performance acoustic panels — they are one of the most deliberately specified components in the system.

277 kg/m³ density
acoustic panel density
8 gaskets per XL unit
≥500Hz peak absorption band

The Density Advantage

Standard acoustic fibrous materials operate at densities between 8 and 80 kg/m³. The Reservoir Mods gasket discs are specified at 277 kg/m³ — a figure that places them in an entirely different performance regime.

At this density, the resistance to airflow through the gasket matrix is extremely high. Energy that cannot move freely is converted to heat. That conversion is the mechanism of attenuation.

The Blend

Wool and polyester contribute different physical properties to the same task. Wool fibre has a natural crimp that creates a highly tortuous internal structure. Polyester adds dimensional stability, ensuring each gasket holds its geometry under repeated cycles without compacting or shifting.

The result is a gasket that performs consistently across the service life of the product, not just when new.

Wool fibres perform most effectively at densities above 500 Hz — the frequency range where surface friction increases and more energy is dissipated as heat per unit of material.

The mechanism is viscous friction. As flow moves through the gasket matrix, vibrating molecules rub against the irregular interstices of the fibre network. That motion converts energy into thermal energy.

Mechanism: ISO 9053 / Delany–Bazley model for fibrous porous materials

Three mechanisms. One gasket.

01
Viscous Friction

Flow forced through the fibre matrix loses kinetic energy to viscous drag.

02
Tortuosity

Wool's natural crimp creates a structurally complex internal path that lengthens the effective route and multiplies opportunities for energy dissipation.

03
Thermal Conversion

The cumulative result of friction and tortuosity is heat: energy is progressively converted and dissipated into the gasket mass.

Performance is often discussed in terms of chamber count or overall volume. Those are meaningful numbers — but the material inside the chambers determines how much work each stage does.

A low-density gasket passes flow relatively freely. A high-density gasket forces that flow to surrender energy before it exits each chamber. At 277 kg/m³, this disc is specified to extract maximum attenuation at every stage.

Gasket Specification

Composition Wool / polyester blend
Bulk density 277 kg/m³
Per XL unit 8 gaskets
Peak band ≥ 500 Hz
Absorption mechanism Viscous / thermal

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