I live in S. Az and had to come up with a faster way to cool a barrel than a wet towel wrapped around the barrel.
The easiest way I have found is to use CO2. You can cool after each shot to simulate hunting conditions. Or you can cool after any number you prefer and really speed up load workups. If waiting isn't for you this is the fastest way to get the barrel back to ambient temperature.
CO2 needs a regulator with plenty of flow. A small rubber hose with end cut at a taper will fit into most chambers for snug fit.