Back in the 90’s when George Kellgren was leading Grendel Arms, he came up with the idea for a bullpup high capacity pump shotgun. Sound familiar? This is not the KSG we know today. The KSG is a dual magazine tube fed pump shotgun chambered in 12 gauge. The predecessor to that concept was the GSG-41. Or Grendel ShotGun .410. It is a .410 shotgun. According to this image/flyer below, the GSG is fed by a 12 rd selectable column magazine. Not sure what “selectable column” means, but is sounds like the user could load one column with bird shot and the other column with slugs. Similar in concept to the KSG, where the user could choose the next round on demand. Another interesting feature is that they designed it to have an integrated flashlight right above the muzzle. Way ahead of the KRISS Vector or the UTS-15.
Due to the bullpup design, the GSG-41 sported a 24″ bbl. Very impressive for a 26″ OAL gun.
Unfortunately the gun never took off beyond concept and possibly a prototype.