Here's the mp5k I rigged up for my xgf, at the moment there's something wrong with it but I have that same A3 metal body and receiver on the way to my house right now so after I get that the gun is getting stripped and completely fixed up.
Note the gun 1st started off as a normal mp5k, but then I bought the PDW stock afterwards. Would of been a lot cheaper to just buy a mp5k pdw to start with.
Here's the list of stuff that went into it.
Stonger spring - shoots about 380 fps on .20's
after market hop-up rubber
Eg-1000 motor
9.6v batter (hidden inside the pdw stock)
metal bushings and what not
longer inner barrel, can't remember how long it really is.
and a silencer to hid that barrel.
here's the photos, thought I'm thinking I'm just going to sell that ris rail I have on it and just stick with the stock front end.
This is the silencer that is on the gun
http://www.wgcshop.com/pcart/shopper..._cat_Silencers