Retro Arms SiCr spring with a progressive irregular coil M140

Retro Arms SiCr M140 Spring with Progressive Irregular Coil

Main spring made of chromium-silicon steel, designed for AEG replicas.
The progressive coil makes it easier to compress the spring without sacrificing power.
Spring dimensions:
Internal: 11.3 mm
External: 14.5 mm
Length: 175 mm