I have fired the predecessor, the M2 60mm. It was replaced by this M224.
It is a very simple weapon, and not a whole lot that can go wrong.
Just pull the safety from the shell, place it into the top of the tube, let it go, and get yadamnself out of the way.
The shell hits the firing pin that sits the bottom of the tube, so off she goes.
Unless, that is, you have a misfire, in which case the standard procedure is that someone has to pick up the bottom of the tube while two other people get ready to very-very-carefully catch the round while the first person very-very-slowly tilts the tube up so that the misfired round can slide out into their waiting hands.
It is a scary situation that never gets any less scary no matter how many times you do it.
What I really remember is the ammunition. The old ammunition was dirt cheap and we were given a lot of it. The new ammunition cost about 60-70% more and our training allotment went down by the same. I remember a manufacturing rep telling us that the dud rate for the old stuff was about 3-5% and the new ammunition was 1%. But here was the friction, if the old ammunition was bad- it was bad (you could throw a dud in the back of your pick-up truck and use it as a wheel chock). If new ammunition didn't work, you had to treat it with caution. My mortar chief asked the rep, to give us the old stuff, plus 5 rounds per hundred and call it even.