Wayne said:

One thing that people miss is the fact that many 1/2" impacts call
for a 1/2" hose. That and the standard quick coupling used is just
like adding a flow control. In the average situation with 3/8" hose
and quick couplings you'll have to run a higher pressure than the gun
is rated for just to get the rated pressure at the gun when it's
running.

The way to check this is by the pressure drop. Put a pressure gage at
the end of the air delivery line at, or near, the gun (or screwdriver,
etc.) and observe the difference between pressure at rest and pressure
running. On a well designed and operating system you should see very
little difference. I'd tell my customers if they saw 5 pounds or
higher drop they needed to attend to either the capacity of the
compressor or the diameter of the air lines (etc.) for the machine. It
was surprising to me how many problems were "restriction" related on
machines which previously had no such problem.

dennis
in nca