How do they work then?
They sound like a nice idea, and they actually fire a projectile....
IIRC...
The mortar itself is just a tube with an opening hatch at the bottom - no firing pin.
The mortar round is metal tube with one end sealed except for a small hole in the bottom.
The pyro itself has two stages - a thermobaric and a bang. The 'round' is pre-prepared with the pyro inserted into the metal tube, it's fuse poking out from the small hole.
In use - a round is removed from the ammo tin, fuse struck and dropped into the mortar, the weight of the outer (reusable) tube sends it straight to the bottom.
Bang goes off projecting the pyro out of the mortar leaving the round tube inside (recovered by opening the hatch).
A seven second fuse is now burning in the pyro (it has been projected by a bang and is not being propelled like a rocket).
Pyro lands on the ground, fuse burns to thermobaric - thwump. As the fuse time is fixed, the thermobaric may go off in the air but in actual use seems to lie on the ground for long enough to dash for cover, the angle of trajectory and therefore time in the air being the determining factor.
It did work very well in-game - the glee of being a member of the mortar crew and lobbing pyro at the enemy being tempered by having to lug a pigging heavy mortar and ammo box around!
