Halo 5: Guardians
73 Achievements
1,250
44-56h
Bringing in the Big Guns
Called in a REQ that costs 5 Energy or more.
10
19.74%
How to unlock the Bringing in the Big Guns achievement in Halo 5: Guardians - Definitive Guide
This can be found under Multiplayer -> Warzone -> Warzone again.
To get to Level 5 reqs you have to kill enemies, capture bases, kill bosses and get your team's score up. Level 5 is a fairly common level in Warzone so should appear half-way or near the end.
When it does, an announcer will say the Level 5 reqs are unlocked.
At that point get yourself killed and press to use req cards. The SAW is a fairly common level 5 card however there are other cards that are level 5 like the Wraith.
If you want to check a cards level, highlight it and press it should say the number there. Once you use the Level 5 card the achievement will unlock.
As a side note once you use a req card, it will take some time before it loads back up to the top Level.
*Edit: You can also not die and just access a Req store if you are in a base your team controls. They are a big green box that looks a bit like an ATM.
Credit: HolyHa1fDead
During Warzone matches, you will earn Energy by killing enemies, capturing objectives, and killing AI bosses. On the bottom your HUD, you will notice a small green meter with numbers on either side; this is the Energy Level progress bar. Each time you reach a new Level, you will gain 1 Energy Point and Spartan Palmer will announce, "Level [X] REQs available".
Once Level 5 (or higher) REQs are available, you can call them in - provided you have, of course - by visiting REQ Stations around the Warzone map, or by opening the REQ Station manually during the respawn screen. You can easily tell the level of a Requisition by the large number on the face of its card in this menu. Once you choose any Level 5+ REQ, confirm your purchase and the achievement will unlock.