The ports on the breach and the jagged end allow you to hold the barrel against the door but allow the gasses to escape out the sides instead of into the door. Possibly blowing pieces of the door back at you.
You can get around this with a normal barrel by just not pressing it up against the door.
Plugging the end of a barrel, holding it flush to the door, is never a good idea either. The beaching end eliminates this issue also.
And more importantly it looks cool. :biggrin: