They&#x27;re talking about M2 .50 heavy machine guns; the B-29 didn&#x27;t have what are considered &quot;cannons&quot; (usually 20 mm or more).<p>For the most part, defensive guns on bombers weren&#x27;t all that useful; even with a fire-control computer aiding you, it&#x27;s very hard to hit a (possibly maneuvering) moving plane from another moving plane. It would probably have been better to omit those heavy guns and turrets and to leave those gunners on the ground to save weight, lives, and resources.