130 guns, 20,000 rounds of ammo found in foreclosed CT home

[overthehillvet]

111. time of the list of "E's" and an I

Ignition
explosion
expansion
expulsion

The chamber contains the brass part of the cartridge not allowing it to escape to the rear or deform and fragment. The containment of the explosion by the chamber makes it so that the only place for the hot expanding gasses to go is down the barrel behind the bullet. The bullet driven by these hot expanding gasses continues to gain velocity until it exits the barrel.
When the chamber is not containing the cartridge the expanding hot gasses go in every direction finding the path of least resistance. The case is very often lighter than the bullet so it is pushed away from the bullet by the forces of the explosion. When the brass cartridge is ruptured by this un contained explosion the gasses will blow out the hole because there is no resistance at all.
Yep that is the way it works.