[Madrigal]

Hey, I was looking for some help in building an upgrade list for my new gun. So far, from the thousand or so rounds that I have run through it, it is a really solid build. However, I am looking into replacing the plastic hopup with a metal one, and maybe throwing in a tightbore barrel. Also, when I fire on semi, I can hear a weird spring 'twang' sort of thing. Any suggestions on what it is?