Does anyone know what "golf balls going around us" means in the following context.
An American soldier is looking back over his experience in the WW2. He was a pilot in the US Marines, fighting with the Japanese aircrafts：
We got jumped by 4 or 5 Zeros(Japanese bomber).
My gunner kept firing even though we only had 90 rounds per can. We stayed in formation, golf balls were going around us. We never made it to the carriers, because the further we went the more Zeros there were.
I found a site that says golfball is a slang for tracers. However, this air battle occured in the morning, so I think there must be another meaning.
Does anyone have any idea about this phrase?