Halo 5 CSR

I need a little enlightenment on the halo 5 placement games. My friends and i were playing breakdown to get ranked, We all played the same amount of games and have the same record, but we all got placed in different divisions, Same with my slayer placements. I got placed in Plat1 with a 9-1 record but another friend went 6-4 and got Diamond1. How does the rank system work or is there a bug or something??

Depends on who you play against, not just record.

We were playing together and got placed differently