Sig 552 hop up problem
 

Ok, so I recently upgraded my TM sig 552, took apart the hop up chamber to put in a new tightbore barrel and put it all back together to install the barrel, and now when I try to adjust my hopup it dosnt work anymore, when I set my hopup to full it fires just like it hasnt even been turning on. Now im assuming I put it back together wrong, but has anyone else had this problem?

Not that I'm totally familiar with opening a Sig but it sounds like you've probably lost the little "nub" that is pushed down when you turn the hop-up higher. Not uncommon when changing a barrel. The way to check this is to pull the barrel out of the gun and look down the barrel. While turning the hop-up "on and off", if you don't see a little protrustion then you've probably lost the little "nub" that puts the spin on the BB. Find it or get a new one and make sure you put it in the right way.

Is the little nub a sort of hollow rubber cylinder? If so this is the piece that I thought I had lost but I recently found on my floor. So if i reinsert this then it should work again correct?

That would be the one. It is supposed to go on the outside of the hop-up rubber.