as far as i know of it's metal, mine is at my dad's otherwise i would look.
but the only piece i can think of that was plastic was that recoil spring guide rod, that is just what i am calliing it, not sure if that is correct or not, once i find my manuel i'll look it up.
I found another message board post on the net that may or may not help
http://www.e-gunparts.com/forum/read...qt=54476&cat=5
let me know if it helps or not please.