8 Player Groups Available?

Went up against a "KDM" group who was pretty good tonight, but I noticed there were 7-8 of them (counted more than 6) and didn't think much of it, but some people on my team said they're notorious for joining up together, but it was the normal BF breakthrough queue, not a browsable server. My question is: how can this be done? Since I don't see an option for it in the menus for my party.