CSR and other Questions

Hey guys. I have been away from Halo 4 for a few months and I was wondering if some of you would fill me in on whats changed. I know CSR came out but id really like to know how it fully works. Im sure theres something on the main Waypoint page but id rather hear from the players. As well were there any weapon setting changes and how are the Majestic and Crimson maps?

This explains what csr is in halo 4

http://www.halocouncil.com/2013/04/11/competitive-skill-ranking/