To add on to what PsyHalceFire said, you can actually get it playing solo!!

1) Enable the console in the game settings
2) Choose: Play -> Wager Match and get "could not join match" error
3) Open console with "~" and type "\g_gametype game" first then \map mp_array.

Once your in the game, use these 2 commands:

/party_minplayers 1 (This enables the game to start with just 1 player)
/scr_gun_timelimit 1 (This reduces the game time to 1 minute for fast rounds)

Once you've typed these commands, restart the map using /map_restart for the above commands to take effect. Now you just need to wait out 5 rounds and bam you get the achievo in 5 mins without needing anyone else to join. I've posted this in multiple other groups aswell.

Well it's as simple as using two commands:
https://steamproxy.com/sharedfiles/filedetails/?id=1544800312

1 - create a private match with w/e configs you want
2 - inside the game, open the console and type /g_gametype ___
with ___ being one of the game modes, for wager its those:
sas -> stick and stones
gun -> gun mode
shp -> sharpshooter
oic -> one in the chamber
so if for example you want to play gun mode, type: "/g_gametype gun" in the console, without the quotes
3 - type "map_restart" in the console and now the map will restart in the mode you choose

Dead, otherwise post on the Mac fix forum.

Is anyone going to do this on the mac version or is this dead?

right now the only way is to use the mac version of the game to get the achievement