105 m/s FPS spring has been calibrated on 363 mm inner barrel and gearbox with type D cylinder (for barrels from 301 to 400 mm). Of course with shorter or longer barrel the performance will decrease or increase, therefore the calibration will be harder or softer. In the calibration process has not been taken in consideration the thickness due to the bearings of the spring guide and of the piston head. So starting by equal initial conditions you have to take into account of a performance increase of about 2.5 m/s for each bearing. The FPS spring is 100% Made in Italy and it is produced in collaboration with leading companies in the sector.