A fume extractor similar in function to those used on some tank cannon would be fitted to the barrel of the machine gun. As a round passes the fume extractor a portion of the high pressure gas enters the fume extractor cavity. After the round clears the muzzle the gas in the fume extractor cavity rushes out towards the muzzle drawing air through the bore and cooling the barrel. The design and placement of the fume extractor is such that negative pressure at the breech happens as the spent cartridge is pulled out allowing air to enter the bore.
-- hangingchad, Jan 29 2006

Air-cooled machine guns are nothing new.
-- DrCurry, Jan 29 2006


Cooling the inside of the barrel is new. At least it's new to me. Instead of [hot gas, hot gas, hot gas] we would have [hot gas, air, hot gas, air, hot gas, air].
-- hangingchad, Jan 30 2006


//allowing air to enter the bore// - just breathe in.
-- xenzag, Jan 31 2006


Leave it to the military industrial complex.
-- moomintroll, Jan 31 2006


Hot - cold - hot - cold = thermal fatigue = cracking and other nastiness. It would need to be carefully regulated to provide just the right amount of cooling (Gatling guns have the multiple spinning barrel idea to do the same thing)
-- neutrinos_shadow, Jan 31 2006


I propose that every other bullet could be pushed out of the barrel using a spring. The cool bullet would draw air in behind it via the Bernoulli effect. Bullets could be picked up later and fired, or every other bullet could be made out of some very cold material instead of the usual bullet material, then simply left on the ground.
-- bungston, Feb 01 2006


// or every other bullet could be made out of some very cold material//

We must not have taken the same science classes, but wouldn't a very cold material heat up to room temperature without refrigeration?

Hmm... a Magazine fridge for cooling the bullets ahead of time....
-- ye_river_xiv, Sep 04 2006



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