NGRS Spring SiCr with Progressive Wiring – M140

Retro Arms Spring for Next Generation Recoil System (NGRS) Tokyo Marui Rifles

The spring is a fundamental part of the gearbox because its strength, along with the air seal, affects the overall performance of the rifle. Low-quality springs, although they often have above-average performance compared to their rated value, quickly lose their stiffness, shorten, or in extreme cases, can break (due to storing the rifle with a compressed spring or in a pre-cocked state).
From the workshop of Retro Arms, famous for their quality CNC gearboxes, comes another finely tuned upgrade part for Marui NGRS: a high-quality spring made from valve wire alloyed with silicon and chromium (SiCr) that retains its stiffness after thousands of shots and does not deform.
Progressive (variable) winding makes the compression easier in the first phase of the piston movement while not reducing the performance. The outer diameter of the spring is 13.75 mm.
The rated value of M120 corresponds to a speed of 120 m/s with an average barrel length. With a good air seal or a longer barrel, the performance will be higher.

Installation

When installing a spring with progressive winding, the compressed part (where the coils are closer together) goes on the spring guide. Retro Arms marked this spot with color for easy identification of the spring strength (see below).

Compatibility

This spring is compatible only with TM Next-Generation Recoil gearboxes (referred to as gearbox v.9) and is not intended for other types of gearboxes.
In terms of length and diameter, it matches the springs of VFC Umarex MP7 AEG and LCT QM,..