might be either a seal issue at the hop or the piston skirt isnt lubed. it's shooting the same fps as my NPAS fitted that i had in previously, so I've imagine it's a boost on the standard nozzle. regardless of not hitting 500 fps with my current setup, i think it's a fantastic nozzle. The adjustment is rock solid so it should give consistency as good as a none adjustable nozzle at the rocket valve part at least. It's shooting 430 on a .20 which is 1.73 joules if i calculated correctly. 380'ish on a .32 which is closer to 2.2 joules.