So a while back, a pretty fantastic thread was created discussing Japanese weapons for future campaigns, and listed among the shotguns was the Murata single shot shotgun. It was listed as a 12ga and I didn’t think much of it, but having taken notice of the image, there was a variant of the product offered in 8ga. This 8ga shotgun was 1500 momme or 5.625kg and would of course use 8ga shotgun shells.
8ga is fairly notable, since that is a substantial increase in the potency of a shotgun, and would do much to compensate for the fact it only fires 1 shot before having to reload. This also opens up a few options, given how such products were provided and sold, and what in-game shotguns are using for pellets.
The first option, which would be in some ways the simplest, would be to offer the 8ga shotgun with slug ammunition. This would more or less turn the Murata 8ga shotgun into a 21mm Berdan analogue.
So we know from datamining that shotguns such as the Browning Auto 5 are firing 18 pellets at around 2.25 base damage each. Since #1 buckshot can only fit 12-16 pellets, the largest (and thus fewest) pellets this could qualify as would be #2 buckshot.
We also know the mass of a pellet, and thus the pellets per ounce of each size of buckshot, as well as the mass of shot for Japanese 8ga shotgun shells (15-20 momme per 8ga shell or 1.98-2.65 ounces). The 8ga shotgun could therefore accommodate for roughly 28-37 pellets. Considering that each pellet in-game has a base damage of 2.25, this sets a base damage from anywhere between 63 on the lower count to up to 83.25 on the higher end.
Overall, there are options, but I think the idea of a single shot doom cannon or Berdan the sequel both sound fairly entertaining either way, and would make for a neat event style weapon.
Observant eyes might have also noticed there’s a 4ga option, and whatever gun was on the market in Japan at the time that would accept 4ga shells I worry greatly for the customer’s shoulder.