TM MP5 Stock - Massive low fps

[T_A_N_K]

I picked up a used TM MP5 on the forum. Its completely stock. It shoots around 160-180 tops. Don't know why. I have a feeling it hasn't been gamed for at least a year.

Basically, what i want to know is, what possibly iswrong, how much is going to cost, is it worth fixing, or just getting my money back.

[Styrak]

Spring dead? Was it stored with the spring compressed? That would be the first thing to check, and then the airseal, i.e. is tons of air leaking out somewhere.