I worked at Weber Aircraft when they were building the ACES II ejection seat. Huge banner in the building "This is the only part of the aircraft that cannot fail".
Saw some epic footage of test seat failures. The final ejection seat test firing for the Gemini program. Pan of the crowd with lots of military brass observing. Super slow motion footage. The doors blow off first. Due to a failure in the pyrotechnic plumbing the right door failed to blow. The left ejection seat came out beautifully. The right one squished the test dummy against the door.
Another test on a rocket sled. Two seater. The only difference between the two seats was a 1/2 second delay on the back seat initiator so that they didn't hit each other. Screw up in the installation put zero delay initiators in both seats. Canopy blows off, both seats come out and hit, the front seat turns parallel and out runs the rocket sled. They picked up pieces of the $100,000 test dummy over a very wide area.
The ACES II ejection seat was a zero/zero seat. The seat would successfully work at zero speed and zero altitude. If the plane had a serious problem on the ground the seat would get you high enough for the parachute to function. The ejection seat rails were about 4 feet long. When the seat cleared the rails you were doing 250 mph. If you had 1,000 feet of altitude you could eject upside down. Despite the fact that you cleared the rails heading at the ground at 250 mph, sensors detected it and the parachute deployed early.
There were many members of the Webers Booster Club. The only criteria for membership was to go out in a Weber ejection seat. One of the clubs I had no desire to join!