One of the more exciting parts of our job were the occasions when we would be assigned to the arm/de-arm area. There, we would remove all the arming devices and charge the rounds into the guns so they would be hot. This would all happen at the end of the runway prior to take-off; the noise was deafening especially when the B-57 engines were being revved up.
This was particularly exciting on the 50 caliber planes, because we would have to climb up onto the wings of the B-57 with its engines running, remove the tsus fasteners, put a 50 caliber round over the pawl and then button it back up again. Often, the fasteners wouldn't cooperate, and there were some anxious moments in making sure the gun doors were properly buttoned up. On the 20 mil. aircraft, we would charge the round into the gun from a gun door under the wing.
Occasionally, we would have trouble getting a round charged in. When the aircraft returned, we would reinstall arming devices, as needed, and remove any rounds that were chambered in the gun. During every tour of duty, you would hear horror stories of a round being pickled off in the revetment area due to a hot gun.
I don't know how much truth there was to these stories.
Dan English - Phan Rang 1968