Interestingly enough, I saw the beginning of the High Standard Bullpup.
I was visiting in LA in 1967, and just happened to catch the news one night.
They had a report on a Beverly Hills Police detective who had invented a new kind of shotgun for use in raids.
It showed this detective firing an early version he'd built himself, using "I think" a Remington 1100 shotgun.
He was shooting bottles one-handed with the buttplate against the inside of his elbow.
Later, the detective sold the idea to High Standard who finished the development around their "Super-matic" auto shotgun.
It was a good idea, but the weight and bulk, clumsy feel, and price caused most departments to turn it down or only buy a few.
The chronic reliability problems soured serious users quickly and killed it off.