old blackpowder guns

[Timelord]

20Gauge in a high capacity pump format would be much more useful for a prep situation. The 12G is great for static or vehicle action or for use in a fire team/squad, but as you say CH, is heavy and the ammo is bulky for individual on foot use. 20Gauge is still a lot of firepower and has been considered in military circles. It was prototyped but never utilised due to the standard available ammo being 12G and the limited issue of shotguns to military personnel. There was never the will to set up or pay for a new calibre shotgun to be rolled out amongst the Forces.

Also IMO the smaller .410 shotgun is very much underestimated. In reality this is a smoothbore multi-projectile launcher with a longer barrel than a .45 Semi-auto pistol. This longer barrel achieves greater projectile acceleration than a .410 or .45 pistol would. 5xOO buckshot can be squeezed in a .410 cartridge. That is still a lot of firepower from a much smaller and lighter weapon than a 12 or 20 gauge. Alternative loads like flechettes or slug can be used. A 4.10 slug or should we say a .410 bullet fried from a long barrelled gun is no mean slouch!
If the gun was a high capacity pump action it would be ideal and easy to carry. The ammo is pretty small and much more can be carried than the equivalent 12Gauge. A high capacity mag could be designed to hold far more shells than a larger calibre shotgun. The reloading materials including powder are much less than for a large 12G calibre or even a 20G shell. The gun is easier to carry concealed if necessary. The recoil is small and so the gun can be held on target easier for repeat shots.
It is in a way a tool along the same lines as a .38/.357 lever action carbine but in a smooth bore configuration with a more reliable pump action mechanism. It can also be used for the same role as the often admired(or not) .22LR rimfire rifle but is able to do much more and deal out greater damage with its larger calibre. It is obviously also an excellent tool using small shot for hunting smaller game which is more likely in many scenarios.
A pretty good allround preppers weapon that is not readily available but could quite easily be put together by a gunsmith.