[Bartholomew Roberts]

Here is a link to a nice technical explanation of every step of the AR gas system including a nice chart showing peak pressures in the system during firing. If you understand this, it will really help you understand how to troubleshoot an AR.

http://www.ar15.com/forums/topic.html?b=3&f=66&t=266108

[Gewehr98]

But couldn't the function be summed up nicely, to paraphrase George Hill, as:

"The AR-15/M16 Poops Where it Eats"

(And yes, I own a couple AR-15's. They aren't the firearms that see the most range time, however.) ;)