Option 1: Remove the birdcage off, remove 1/2x28 thread protector, clean the threads, put some BLUE loctite on threads and reinstall 1/2x28 thread protector, reinstall birdcage.
Option 2: Remove the birdcage off, remove 1/2x28 thread protector, reinstall birdcage.
Option 3: Remove the birdcage, install the 18-1 thread protector, remove the 1/2x28 and install your choice of 1/2x28 muzzle device.