SHS AEG springs are designed to deliver reliable and consistent FPS output with every shot, helping to increase range and improve your accuracy. The Non-Linear Coil Design: Most stock AEG springs have a ‘Linear’ coil pattern, in which each coil of the spring is equidistant to its neighbouring coils. The coils on SHS’s AEG springs are non-linear and get tighter or closer together toward the rear of the gearbox at the Spring Guide. This allows the spring to ‘cushion’ the gearbox from the force of the piston travelling back and gives it smoother, more consistent, acceleration toward the front of the gearbox; All of this adds up to give your piston a much smoother ride when you’re laying down fire. Smoother piston travel will help to improve your gearbox’s life due to minimizing stress on key components, such as the gearbox casing and spring guide and helps give consistent FPS which gives more accurate shots.
Theoretically provides approximately 350fps
To calculate the approximate FPS from the 'M' number, multiply it by 3.3. (there are 3.3ft in a Metre) eg: An M100 spring should ideally give you 330FPS but it's an approximation that is affected by all the other internal parts of your gun, how worn and/or lubed they are, air seal efficiency and so on.