Rail replacement for M4 S-System JG
 

Hi!
I need a suggestion for I have a M-4 S-System by Jing Gong (I’m a newbie, fer cry sake!) and the front rail, bottom part only, is made by plastic. I’d like to replace this plastic part only, so my question is: who knows a good metallic replacement for this rail? Am I doing something stupid? I mean, is there any reason why this bottom rail must be made by plastic?

I believe all S-System/ S.I.R. rails lower part is plastic. At least everyone that's come through my hands have been! :)

Jeff