Some years back, saw an article on a water-cooled varmint rifle. As I recall, it had a water jacket, and a small pump to circulate the water. Reminded me a bit of the old water-cooled machineguns...
Guy
Powers Custom built those, I recall the article, too............
The big deal ws to keep the pressure the same around the barrel all the time, so impact wouldn't shift (and to cool it down). They (he built at least two) had regulators to manage that pressure, and ran a hose to a big cooler filled with ice and water (48qt. Coleman, or about that size).
