I typically write about Colt items but every once in a while something else catches my eye. This chamber block / chamber flag design is one of those things. It is very unique and seemed to be a great design for what it is. This design is being used by a federal agency that is required to keep the chamber plugged until a situation requires the loading of live rounds.
What I think is great about this design is that you accomplish hands-free removal and chambering of a live round by actuating the charging handle. The shell casing head ensures ejection of the chamber plug by the bolt ejector and the subsequent stripping/loading of a round as the bolt goes back forward.
I ended up talking to someone tonight who is familiar with the design and use. He stated that these chamber flags / chamber blocks can actually cause damage to firing pins. So, although an interesting concept, perhaps it is not a good thing to actually use.
Regardless of your view of the use of chamber plugs, IF you had to use one, this design seems to be the way to go in an operational environment. However, you need to balance the risk of the aformentioned potential risk of firing pin damage.
I also learned that these are made by a company called Safe Tech and are available from Brownells.