[GeeTwo]

Our findings agree with the general consensus that diameter of flow is at least as important as pressure. The key diameter is the smallest orifice between the accumulator tank and the input to the barrel. Ours is 3/4" at the solenoid valve, and with 60 psi of air in the accumulator (a cast iron tank of about 3 to 4 gallons capacity), we can toss a t-shirt from the running track over our stadium's press box - WAY over a 50 foot lateral toss.

In addition to using pressure to adjust the range, we also regulate the "valve time". Our current system opens for 40 or 50 ms; much longer will use a lot more air with little (if any) additional range. Shorter bursts can be used to dynamically shoot shorter range shirts or lighter objects.

It takes a lot of battery to make the amount of compressed air you'll need to fire t-shirts. I'd suggest either having an A/C compressor to fill a storage tank to a higher pressure than your accumulator, or use a scuba tank. Stock scuba regulators bring the pressure down from about 3000 psi to where the regular FRC regulators can fine tune to the 40-60 psi we use in our accumulator (between 100 and 120 psi IIRC).

Finally, let me repeat the warning about PVC (or any other "brittle" material) being used to hold or switch pressurized air. Remember how I said how much energy is needed to compress air? Well, most of that energy is sitting in the tank. If that tank or a solenoid valve should shatter, there's plenty of energy to accelerate shards to hazardous speeds. Work done by or to a fluid on expansion/compression is ∫PdV or (for constant pressure) PΔV. Water at 60 psi is about 200 parts per million smaller than at ambient; Air at 60 psi is about 800,000 parts per million smaller than at ambient. Because air changes volume so much more than water, compressed air has several thousand times as much energy as a similar volume of compressed water at the same pressure. NO SPRINKLER VALVES!