honestly there isnt anything you can do with the crappy clear mechbox, and fragile exterior. your best bet is to field it as is and save up for a better gun. I can pretty much guarantee that if you put in a stiffer spring the mechbox would explode and if you take apart the body some things gonna snap...
"You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here."