The 120 m / s FPS spring has been calibrated on 363 mm barrels and gearbox with type D cylinder (for barrels from 301 to 400 mm). Of course, with shorter or longer barrels the performance will decrease or increase, so you will switch to the harder or softer calibration. The thickness due to the spring guide and piston head bearings was not taken into account in the calibration process. For this reason, with the initial conditions being equal, a performance increase of about 2.5 m / s must be taken into account for each bearing. The FPS spring is 100% Made in Italy and was created in collaboration with leading companies in the sector.