The U.S. Customs office in San Francisco had purchased a bunch of 916a riot guns before I came into the service. Once I became the lead firearms instructor, I had told the office Chief that they were junk and should be replaced. He said he had never heard of any problems with them.
So on the next quarterly qualification, I set a simple tactical shotgun course, and gave the Chief one of the 916a shotguns. By the fifth round, he had three malfunctions. He immediately told me to go buy some Remington 870 shotguns to replace them.
The last time I saw the 916's, they were being dropped overboard one of the Customs boats a few miles outside the Golden gate. Now Davy Jones has them in his locker.