I was watching a vet recall Dday and he mentioned waiting for a gap when gunners had to change barrels due to excessive firing before lowering the landing ramp. I’m not doubting the guy at all but I’ve never heard of barrel changing , just overheating and having to cool down. But then again I’m not well researched I’m this field at all so it would be cool to know, did Allies actually wait for Germans to have to change their barrels sometimes or do you think that may have been something a higher officer told the guy that a pause in fire could be and time to go ?