Do I need to install the crush washer with a Flash hider?
It depends on the type of flash suppressor.
For a simple, external-thread flash suppressor, you first need to remove the old one. Take off the collar and unscrew the flash suppressor from the barrel. Make sure that you keep track of all the parts – there are usually several springs and small pieces that can easily get lost.
Next, install the new crush washer by placing it over the threads at the end of the barrel. The lip of the washer should be facing outwards so that it makes contact with the Flash Suppressor when it is screwed on.
Then screw on your new Flash Suppressor adapter, making sure that it’s tight against the crush washer. Test it out to make sure it’s installed correctly and that the barrel is still threaded.
If you have an internal-thread flash suppressor, the process is a little different. First, remove the old flash suppressor by unscrewing it from the inside of the barrel. Again, keep track of all the parts and pieces.