Here’s the Cliff’s Notes version: Their use is strictly forbidden. We bring this up because some fresh .223 brass was recently found in an action bay where no competitions or Law Enforcement training had been recently scheduled.
Anyone discovered engaging in this activity can, at a bare minimum, plan on losing their action range certification. Ignorance of the rules is not an excuse; everyone who is action range certified has had this made perfectly clear to them. Likewise for excuses like “I saw .223 brass on the ground so I thought that it was OK.” Both Law Enforcement training and Club competitions where these firearms are used are regularly scheduled in the Action Range area. These activities are closely supervised. Members who need a refresher on which cartridges are permitted in the Action Range area can look here.