Problem- Halo: Reach Firefight

I try to play Firefight with 2 other friends and it says that we can’t! Why is this, I thought that the point of making Firefight is so that you may play with 3 other people?

Posting a few details of what the problem is might help. Are you trying to do a custom Firefight versus game? Firefight matchmaking?

Also, do you have a 4GB Xbox Slim? They can’t do co-op stuff.