I think it is water cooled.
To accommodate the barrel length, it must be registered in two adjacent counties.
This is the S&W 500 Magnum with a 10" bbl.
S&W offers an "Emergency Kit" that offers a 500 Magnum with a 2" bbl. I guess you use it when you encounter angry grizzly bears, homicidal killer whales and rabid freight trains. If you fire a shot in a densely wooded area. the muzzle blast can be used to clear a small landing pad for helicopters and start a cook fire for the bear.