there is an o-ring on the back piece. it basically makes a secure connection for the front and back. however you cannot shoot through the barrel without an insert. the insert goes in the back all the way to touch the o-ring, therefore making the barrel 100% circular.
if you didnt put an insert in the barrel, the ball would simply blow up when it hit the o-ring
damn good barrels if you use good paint (last use some evil paint and didnt get a single break). ignore what people say about barrels. simply get out there and try other people's barrels. we all were at the same stage you are, so people are more than willing to help. we all want more people in the sport to increase its popularity.
