I read a gizmo that worked similar to this in an old copy of Precision Shooting several years back, (trying to remember the details). It had a cartridge case for the particular rifle that had been drilled and tapped through the web/flash hole to accept a fitting with an air hose attached to it. The other end of the air hose was attached to a bottle of compressed gas (oxygen, carbon dioxide, nitrous oxide, I don't remember which). The high velocity of the compressed gas rapidly cooled the barrel from the inside out.I use a small air pump and a 12v battery pack. In 90° weather I can usually fire a round every minute and the barrel will never get too hot to hold. 45 seconds with air blowing down the barrel from the chamber cools as well as 8-10 minutes with the barrel facing up and the bolt open.
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