Upgrading a TM MP5PDW

[Lord Jebus]

Hey Guys, Been away from the Forums awhile... Years actually!

I bought aTM MP5 PDW off the Classifieds section years back and it still works great. Having bought it used, I have no idea what, if any upgrades have been done.

I have 2 upgrades I want to do... But I need your help.

1. I want to upgrade to a metal body if possible. I've seen them for the A5/A4/SD6's etc. But not for the K/PDW's...

Can anybody tell me if they exist? And If so, Send me a link?
(I've been searching for the last week or so for something but to no avail)

2. I want to modify the Stock on it. Or at the very least replace the butt plate on the body. The stock I have is splitting at the base of it. I have it wrapped in Electrical tap for now. And the strap loop is missing from the swivel. So I want to modify the plate to accept a collapsable stock that would normally be found on something like an M4A1. I've seen pictures but am not sure how they do it. There is almost no room between the plate the and the gearbox. Given the right parts I'm sure I could figure it out though.

Does anybody have an OLD K/PDW back plate they no longer have a need for? I'll buy it.

They other option and this is a bit of a stretch.. I would like to put the collapsable H&K stock from the A5 on there.. The K has the recesses in the body for the stock when it's collapsed but not sure if it will fit properly.

Ohh... And a third thing I need help with.. I've got what I believe to be a G&P Knight's Armament 8" silencer on it and I've always had a small issue with the occasional bb getting stuck in it. I have an idea how to fix the problem. I drove around today to about 7 places... looking for a compression spring and a couple compression springs.. I need 3/8" x 7" or 8" that I can put inside the silencer that would fit inside the sponges and act as a guide for any bb's that decide they want to stray. And that way the silencer still works as a silencer.
I couldn't find ANYTHING. When I was living in BC the auto parts place I worked at had a section of wall devoted to springs.. And I know the size I need exists.

Barring that I am thinking of going to my LHS and getting a Brass tube the diameter I need and "venting" it by cutting multiple slots in it so that the sponges can still absorb the sound.

Any ideas on where to find the spring(s) I'm looking for or critiques on the brass tube idea?