Larry, First, I thank you for your service to our country, your stand on our second amendment rights and my Nighthawk Custom Vickers Tactical I’ve had for almost five years, it functions 100% and is accurate. My question is concerning Crane O Rings, I upgraded my AR with a BCM complete bolt carrier group which came with an uninstalled O ring. I shot my AR without the O ring and it worked perfectly and I shot it about 300 rounds with the O ring and it worked perfect, so I left it in. So is the O ring so beneficial that it needs to be left installed? Thank You for your reply.