Barrel Coaxial

How did WW2 Air Cooled Machine guns stay cool when in some cases covered with a metal sleeve?

I know a lot of WW2 Tank's air cooled hull machine guns and some coaxial machine guns from various nations are exposed without a sleeve or guard. Some air cooled coaxial machine guns I noticed are semi recessed into the mantlet or turret and is the gap left around the diameter of the barrel to allow air to circulate around the barrel.lastly, do any countries during WW2 use fans and air vents to pump air around around air cooled coaxial machine guns. I suppose all of the above might not be necessary as I don't know how fast and how long it takes for a air cooled machine gun barrel to heat up and cool down. Cheers John.

Barrel heating varies from gun to gun. Rate of fire, how many rounds are fired over a given period of time, barrel thickness and the effeciency of the cooling jacket all come into play.

The German MG42 was the worst offender. A barrel change was REQUIRED after just 100 rounds of sustained fire. Tanks usually had heavy barrel versions of the MG34 though.

The American Browning M1919 didn't really have problems with barrel overheating. The ROF was relatively low and the barrel quite thick. If the gunner practiced good fire discipline (bursts only - sustained fire was pretty useless) it probably wasn't an issue.

The gun mountings were snug. Any hole in the armor is a weak point so these were kept as small as possible. I was crawling around an M8 armored car yesterday and the coax M1919 was in the mantlet so tight I wonder if they had to grease it to get it in there In many instances the gun was contained entirely within the vehicle with a small hole only large enough for the bullets to pass in the armor.

500 New F-81 Barrel Coaxial RG6 Connectors RG59 Adapter $99.99

500 New F-81 Barrel Coaxial RG6 Connectors RG59 Adapter $99.99

(50) - New 2.5GHz F81 Coaxial Barrel Couplers $38.99

(50) - New 2.5GHz F81 Coaxial Barrel Couplers $34.99

Cabletron BNC Series Rg58 Female- Female Barrel Connector (Jack-Jack) $19.99 Enterasys Networks provides best-in-class infrastructure solutions to enterprise customers worldwide. With one of the industry's broadest and deepest product portfolios - plus a full range of service and support offerings - Enterasys is uniquely qualified to meet the evolving needs of today's businesses....

USB to 5.5mm 5V DC Barrel Jack Power Cable $3.95 Adapt your USB port with this cable so you can power small devices and electronics that use a 5.5mm barrel jack. Cable uses the 5V DC from the USB port. Length: 1m / 3ft....

USB to 3.5mm Barrel Jack 5V DC Power Cable $3.95 Adapt your USB port with this cable so you can power small devices and electronics that use a 3.5mm barrel jack. Cable uses the 5V DC from the USB port. Can be used with car outlet adapters that have a USB port as well. (Car adapter sold separately.) Length: 1m / 3ft....

10pcs High Frequency 3GHz F81 Barrel Connectors Couplers $5.99 Replace standard/low frequency connectors(white/yellow color) in wall plates and get 3GHz digital broadband performance. Connect and extend two RG6 or RG59 "F"connector coaxial cables. Compatible with all satellite delivery systems and cable TV services. You will receive 10pcs high frequency 3GHz F81 barrel connectors couplers....