When Yossarian and the others return from leave in Italy, after the C-47 touches down on the runway, a shot of the landing gear is inter-cut; however, the landing gear is clearly that of a B-25 which, although prevalent in the show, are not otherwise included in this particular shot.
In most of the flying scenes we see the gun barrels of the .50 caliber Browning machine guns that were mounted in the B-25 nose, but from the interior shots...no machine gun. I am sure they were CGI...all is seen are the barrels. in a real B-25, the bombardier would have manned a real one.