There is bits of metal and powder come out the front with blanks with a BFA/BFU. We got a demonstration using a bit of card at 6ft with one fired without a BFA on. It certainly isn't just hot air that comes out of them there were quite a few holes in the card. I remember them calling them Blank Firing Applicator or some such.
Anyway in my day it was the old school methods of weapon training and it went
1st transgression was a mild shouting at.
2nd huge bollocking.
3rd punch to the face.
But to be fair I can't remember anyone being gash with handling weapons. And there was very few punches handed out and those that were on the receiving end all seemed to deem it a fair cop and for their own good.
One 2lt that got posted in spent quite a lot of time running around with his rifle above his head due to technicality's about assaulting an officer. We all thought we would prefer the punch to be honest.
The idiot left in in the bogs one day, we didn't see him again after that. He may well be at the bottom of a earth toilet. And there was actually a phase 4 of the punishment ladder when Geordie really lost his temper.