Not totally sure on the weight, but it'll probably be a noticeable difference. What you're really going to notice, though, is that the gun is going to get really front heavy. Check out O'Dells Paintball and get the stock barrel bored out to accept Freak inserts. I had it done and it works great. I can put 10 balls on top of each other without even thinking about it. I couldn't hit a damn thing with the stock barrel before that with that awkward detent ring setup.
Here's his website:
O'Dells Paintball
Shoot him an email asking for your barrel to get bored. He does it for $30 and includes return shipping. I sent mine on a Monday and had it back Friday so I could use it. Awesome guy.