Notes: This is basically a 73mm gun of the same type as on the BMP-1 and BMD-1, mounted on the carriage of the ZPU-23 antiaircraft gun. This was done to make use of guns on BMP-1s otherwise made inoperable due to age or other mechanical problems. The BPTU-23 retains the sights of the BMP-1 (+1), and has an AV2 gun shield to the front to protect the crew. When in use, the wheels are raised off the ground and the gun rests on jacks. The gun is fed from a 12-round drum that is manually actuated.