I'm not upgrading it, i'm fixing it. It has no Mechbox so I just want to put a mechbox in it. any suggestions? bottem line i just want it working so I can use it while my M4 is out.

He's saying it would be cheaper to buy a new, actually decent gun.

no guns for kids

I know it is, but I'm a very stubborn man and want to keep my SD6, I had great times with is (nothing sexual...) so one last question, I was browsing the forums and I read somewhere that is is ilegal to import a M4 lower but legal for an m4 upper but legal for MP5 lower and ilegal for MP5 upper... is this true?

law restricts the part of the gun with the serial number on it in real steel, M4 is lower and MP5 is upper iirc, still no guns for kids tho.

So I can import a MP5 lower receiver from an international retailer?