That's definitely lower than usual, I run my SMP at ~90 psi and get approximately 385fps with .25 gram bbs. Check the alignment of the nozzle in the hopup and also check your hopup bucking, from the sounds of it there's probably a poor air-seal somewhere. Also, think about joining the Wolverine Airsoft Owners page on Facebook, they're extremely helpful and there's a huge amount of knowledge on that page that can fix any problem.