S/Sgt. Benjamin Franklin Warmer III flew 50 missions as waist gunner on B-17s with the 348BS, 99BG. On 5-Jul-1943, the 15AAF sent three heavy bombardment groups to carpet bomb Gerbini Aerodrome. They were met by more than 100 Me-109, FW 190, and Macchi 202 fighters. The Group was awarded a PUC for the mission. Debriefing revealed that S/Sgt. Warmer had shot down 7 enemy airplanes, for which he was awarded the DSC.
Total claims by gunners of the combined groups was 45 enemy planes. An airman who had bailed out on the mission, been captured by the Italians, and subsequently escaped, reported "the Italians told us we shot down 51 of their planes in that fight."
Having read hundreds of mission reports, and dozens of individual bomber debriefing reports for each mission, I'll attest to occasionally reading gunners visually following enemy fighters all the way to the ground. Also, those debriefing reports "allowed" much fewer than half the claims of enemy planes shot down.
S/Sgt. Warmer wasn't the only bomber gunner to be awarded 7 "kills" in one mission. In China, 14AAF 308BG 374BS flight engineer/gunner T/Sgt. Arthur Benko - the Ace of Aces of WWII bomber gunners - was credited with 18 enemy aircraft on four of his missions. He was written up in Time Magazine and National Geographic. Benko was a champion competition rifleman before the war, so he knew how to lead a target. After claiming 9 aerial victories on the first two missions that were met aerial opposition, an observer was sent to accompany him. On 1-Oct-1943, he shot down 7 Japanese interceptors. He shot down another 2, two weeks later. On that mission, he and most of the crew bailed out when their B-24 lost two engines. Benko and 1st Lt. Malcolm Sanders, the bombardier, landed in a river or were captured by the Japanese, and are MIA. (In 2009, Benko was "recognized" for 7 victories in one mission with the awarding of a Silver Star).