Wow. I mean, making a functional mortar just is not that hard. Any competent engineer or person with any mechanical skills in the US could make one out of stuff you can buy in any gun shop and hardware store.
—”Wow. I mean, making a functional mortar just is not that hard.”
But it does require standard dimensions of all components... like the OD of the fins centered on the firing pin and overall OD so the round drops smoothly down the tube.
That said some of the rounds do fire, an extended hangfire of the dud round on the pile might scare the crew away. for a very long time.