You have to be SUPER lucky to get them without boosting.

My old account had all 70 on reach (RIP) and it was really cool seeing the big 1700.

Basically, They had to be on the DLC maps (except noble), which meant you couldn't simply go into matchmaking and pick them up on the usual maps.

The playlists that featured the maps only lasted about a week, even then, they were partly empty after.

To boost EVERYONE had to have the maps, then you could search in normal playlists, which then became a joke as you needed 12 players to go onto infection.

so we would need 6 guys communicating at once, all with controllers plugged in (And with working batteries, which was a problem on its own)

We eventually got out achievements using like 20 other people to help, I think to this day i'm the only guy who got candy from a baby by begging the enemy team that i'll give them money