I use one of those battery powered air pumps, the ones for inflating air mattresses and such, to cool the barrel down. I have a piece of hose that I run from the nozle up tight into the bore... turn the air on, and wet down the barrel... it'll cool it in about 5 min. I started using it at the range when testing loads and the next time I went there were 3 guys who'd coppied my set-up... all of them complimented on how quickly the pipes cooled down... I should be getting royalties for it.