[GeeTwo]

I'm one of the ones who suggested a 3/4" port minimum. This is based on a 60 psi working pressure, and looking for "top row of high school bleachers (home side) from the running track" performance. If you can settle for less performance than this, or can boost your pressure, you should be able to make 1/2" work for you.

The suggestion by PAR_WIG1350 and endorsed by juju_beans is essentially a second tank. You may want to consider using a length of large steel pipe that is capped at one end and has reducers down to 1" or 3/4" at the other end AS a tank. For purposes of calculating the needed volume, our accumulator tank is roughly the size of a scuba tank, though it's a cast-iron beast with a working pressure (from the painted-over plate) of 150 psi. I suspect this is actually a good bit more than we need; we only need to open our solenoid valve for 50ms to get our good shot. Opening for longer provides only modest improvement.

While I don't have any specific numbers handy, according to our tests a few years ago, barrel length is a "optimal length" parameter -- a barrel needs to be long enough to apply the air pressure to the shirts for a suitable duration, but if the barrel is too long (at least given a constant tank size and pressure), friction causes a long barrel to give a reduced range.

OK, specifically, but based on memory not notes -- IIRC, for a 2" i.d. barrel, 60 psi, 3/4" valve and larger lines, the optimum length was between 30" and 40; I believe we used 36".

When we increased our barrels diameter to 2.5" i.d., we reduced our barrel length to about 24" to keep the barrel volume roughly constant (based on work being equal to PΔV, not calibrated by measurements, but it worked OK for us).