Spandau aircooled MG jacket?

[cbk57]

Pardon my ignorance but I just don't see that the jacket on the Spandau air-cooled MG served any real purpose.  It looks like it blocked air flow not aided it.  Was it a barrel stiffener?  What about the jacket on the Vickers on the Sopwith Pup and the like.  The large non perforated jacket looks like it would hinder any air cooling. 

Thanks

[cbk57]

Thanks, I did not think of the heat sink concept.

[GHE]

Messieurs !

Further info at the topic "weapons-props .."

Gunther