Originally Posted by
GeeRam
Early E and F models did have 7.92mm MG17 machine guns fitted, as did very early version of the Fw190, but by the time the USAAF started its missions in earnest in 1943, the Bf109 and Fw190 in service were all fitted with various combinations of the 13mm MG131 heavy mg, and MG151 20mm cannons.
The 13mm was reportedly adopted as a counter to the large US bombers. They replaced the 7.92mm in the Bf109 from spring 1943, and those in the Fw190 models in November 1943. Until those new models were available in numbers, then the older 7.92mm were still around. The 338th was first in action in May 1943, so plenty of 7.92mm around for some time still, to have hit those goggles.