that pencil up the spout trick has killed a few.
Our PSI who was ex Falkland's and other things said that if he ever heard of one of us doing it he would hunt us down and break both our index fingers so that someone else had to wipe our arses for the next 4 weeks.
I to be perfectly honest I don't think he was joking. He didn't joke about these things including removing the pistol grip off a SMG for room clearing purposes. Which he even showed us with live ammo. Seemed quite effective to be honest with a full clip and it lobbed round a doorway with the working parts held back.