[mutelight]

Looks interesting. In fact I have tried some out myself.

Xbox 360: How to Create a Custom Halo 3 Match and Get All Pistoly - Kotaku

First, get six to eight other players in a game with you in the pre-matchmaking phase.

After you've assembled this group, have a separate player matchmaking by themselves send the party leader an invite.

The party leader needs to bring the party to the new game, but one person will get kicked.

The person who was booted will now send invites to those who weren't booted -- it is possible you'll have to repeat these first couple of steps because you need two people in the custom game lobby.

Now you should have a party of two and a party of six in two separate lobbies -- the party of six invites the party of two into their game.

Someone in the party of two should lag out into a custom game that actually works.

[Peter]

interesting.
Is that how the "Sniper and Shotgun" mode is selected?

[mutelight]

That is actually in the matchmaking playlists already.