Back in 2007/08 a company called Monolith Arms was promoting a pump-action 12 gauge shotgun they designed. The shotgun was notable because it fed from a horizontally mounted magazine inspired by the FN P90. They shotgun was promised to be on sale in 2007, when they did not ship it in 2007 they promised it in 2008, but again it never materialized.
Maybe Monolith Arms were just a little to early to the market. There is a lot of interest in high-capacity shotguns these days, for example the Kel-Tec KSG, and a number of high-capacity solutions for regular shotguns such as the MD-20 drum magazine for the Saiga-12. It would sell well today.
Back in early 2008 the company released this teaser video of the shotgun …
Many thanks to Jacob for the photos.