Once the AC-47D gunship proved itself in preliminary trials in action over South Vietnam, the USAF pressed ahead to convert more C-47s into gunships. However, the 7.62mm minigun used on the AC-47D was just starting production and were in short supply. As an interim measure, it was decided to use as an interim gun the Browning M2 .30 caliber gun which were in storage at a warehouse at McClellan AFB in Sacramento. The firing solenoids for the guns were in very short supply, so for the M2-armed prototype AC-47, the solenoids from the B-24 "Strawberry Bitch" on display at the USAF Museum were borrowed. It's been said that that B-24 is still missing those solenoids.
Source: Gunships: The History of Spooky, Shadow, Stinger, and Spectre by Wayne Mutza. Specialty Press, 2009, p30.