I keep seeing threads about people installing new inner barrels for their weapon of choice.
I can't seem to quite understand the purpose of these, though, but a lot of people seem to like to have them installed. What exactly is the difference between different kinds of inner barrels, and what is the general idea of what they are supposed to do?
Also, I sometimes see people talking about outer barrels. I haven't got a clue about what these are, or what they are even for.
Just looking for some advice on what they are for future upgrades on my own gear.