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If you’re looking for a clan/community, It’d be awesome if you joined Forerunner Conflict (fcwars.net). We’ve been going for almost 9 years now, since Halo 2, and as a war simulated community with around 45-50 active members, there is a lot of interesting things we can offer.
The main thing is that the community itself is split into two armies: REDD and BLUE. REDD would be the equivalent of the empire and BLUE is the equivalent of the rebels/exiles. Each Sunday at 6PM EST, REDD and BLUE play against each other in an effort to take control of the two different maps being played. The armies are split into squads, which are essentially small teams of 6-10 players. I’m currently creating a squad, and I can tell that you’d be very beneficial to the whole process.
I’ve tried to just summarise the main points of the community, but if you need more info, message me on XBL. Gamertag: Barry Soap
Thanks for reading 
Hey Pdoubl3kill, if you have a Facebook account, you should check out the community I own, called Halo 3 Lives On! With almost 1,250 members, I’m sure you’ll find at least a few gamers to run matchmaking with, myself included. Here is the url for quick access: facebook.com/groups/needz.moar.h3
Best of luck,
Piffin