8mm Metal Gearbox Shells for M4/M16/SCAR/MP5/G3 Reinforced G Series&G

The FPS spring from 100 m/s was calibrated on rods from 363 mm e gearbox con cilindro type D (for rods 301 a 400 mm).
Of course, with shorter or longer barrels the performance will decrease or increase, so you will move on to the harder or softer calibration.
The thickness due to the spring guide and piston head bearings was not taken into consideration in the calibration process.
For this reason, given the same initial conditions, an increase in performance of approximately must be taken into account 2.5 m/s for each bearing.
The FPS spring is 100% Made in Italy and was created in collaboration with leading companies in the sector.