I used an aks-74 version last time I was on a field whenever I was in the safe zone, and I had no problems. I asked the event runners beforehand if it was okay of course. I would assume a case designed to hold a real Kalashnikov safely whilst jumping out of an aircraft would be just as effective as a barrel condom.
Are you going to carry that thing with you on the field?
Seriously, people, it's not that difficult. Buy a barrel condom or three and call it a day. We will NOT let you on the field without one.