There were two plastic thread protectors made for the Swedish Mausers that have the "B" threaded barrel. One is like a simple short tube that is open at both ends, and the other is closed at one end.
The Swedes used wooden bullets for Combat training. They were not supposed to be fired at anyone at less than 100 meters, but accidents do happen. A Blank Firing Adaptor was issued for this Combat training, and there are blades inside the adapter that shred the bullet and blows the wooden pieces out through holes in the side of the Adaptor.
Because of these blades inside the BFA, if a live round is fired through it, it will hit the shredding blades. and can cause severe destruction to the BFA, the rifle and the shooter.
There are threaded metal sleeves available that can be screwed onto the end of the barrel to protect the threads. If you can not find one, check on E-Bay.
