The Answer

The Answer is a special variant of the M739 SAW featured in Halo 5: Guardians.

Campaign
The Answer can be found on Mission 13 of Halo 5: Guardians as an Easter Egg.

Warzone
The Answer can be obtained for Warzone use by using REQ packs.

Changes from the M739 SAW

 * Increased accuracy at the cost of slower rate of fire
 * Increased damage