https://upload.wikimedia.org/wikipedia/commons/8/8f/%E7%AC%AC15%E6%99%AE%E9%80%9A%E7%A7%91%E9%80%A3%E9%9A%8A%E7%AC%AC2%E4%B8%AD%E9%9A%8A%E3%81%AB%E9%85%8D%E5%82%99%E3%81%95%E3%82%8C%E3%81%9F96%E5%BC%8F%E8%A3%85%E8%BC%AA%E8%A3%85%E7%94%B2%E8%BB%8A.JPG
銃口近くでのバレルの外径が約1.3インチ、33mm程度
http://www.pt103.com/PT_Boat_Components_Browning_50_Cal_M2_Aircraft.html

https://i.imgur.com/iTb91Mr.jpg
ペラッペラやぞペラッペラ