Blunderbuss/Musket

Requires propellant. Expanding gas is the most common at present but liquid being forced from an extradimensional location (modified macerator?) could be just as or more potent due to the lack of compressability.

Needs a trigger that can be activated from outside the containment tube. Maybe some kind of tripwire? This would be something for those that have done seal research to figure out.

So I am a longtime lurker and first time poster. This post is meant primarily to outline the practical problems that need to be worked out for several basic types of firearm to actually be made.Thats essentially it. Ammo is obviously universal to all of these designs and at their core these simple firearms are nothing more than a tube, propellant and trigger. The problem children will be semi-automatic or automatic firearms where ammo feed and propellant ejection can't be done between shots by the user.An all in one projectile/propellant combo would help immensely here as it allows us to draw on the massive repertoire of modern fire arm design.That being said most of the gap between modern firearms and the simple ones provided above is actually in metallurgy. The spring steels and highly pressure resistant alloys needed for chambers and barrels simply do not exist in this world and may not for centuries due to the lack of consumer markets for ancilliary items that use these alloys.We also need to kick off the industrial revolution here. It needs to occur to get precision parts so that maintenance is not prohibitively expensive. In addition if our goal is to arm civilians, mass production needs to be standardized to make these guns in any sort of meaningful number.To be clear this post is not meant to discourage. To the contrary, it is meant to direct minds off of the relatively simple, though time consuming to research, prototype and towards mass production.