There are a couple threads about the differences over on M4C...even one from our very own @ASH556
0.60-.075 is optimal. when you shorten the barrel, sometimes its best to have the port opened to .080-.090 but then you start getting a little gas in the face when the BCG cycles and ejects the shell
thanks, I'll have to check that out . So PSA uses a gas block that is not adjustable or what makes it inferior to others?