I am not sure about the longevity of the PVC deal but my buddy who
built one says when it gets louder, you just replace the caps. It is
BB gun loud with regular .22 LR ammo out of a 4-5" Ruger bull barrel.
I think it is quieter than my CO2 pistol. That is probably because a
significant amount of powder is still burning when the bullet comes
out. They say the same thing about the SOCOM M1A