>>64232380
The US had a few different .60 cal guns, including some meant for aircraft. Largely dead ends, you inherit a lot of the challenges of the heavier 20mm-class weapons without the corresponding HE capability. That being said I'd be interested in trying to make a new and viable design for a late-war aircraft cannon in Rixas
https://www.secretprojects.co.uk/threads/usaaf-0-60-caliber-machine-gun.14481/
https://archive.org/details/TM9213A20mmT160.60T130/mode/2up