Chris comments

Something is off.

To build a blackpowder base canon (the homemade device is more akin to canon rather than shotgun), one need: propellant (blackpowder), projectiles, device (the homemade metal tubing), and trigger device (probably using electric ignition).

Basically, the procedure is

First, insert the propellant to the end of tube.

Second, insert the projectiles to the end of tube, sitting on top of the propellant.

Three, insert stopper (can be some kind of paper, or cotton, to prevent all the ingredients from falling out).

For an experimental homemade weapon, one has to do a lot of trial and error to find the right amount of propellant and suitable projectiles, to achieve accuracy and finding the lethal distance of usage.

Can a regular person just researched all this within a couple of months, and

Able to build these experimental weapon to a functional capacity and familiarize himself with them;

Possess the familiarity of the tactical movement to overcome loud noises and chaos;

doing all these alone without any help and training?