Not a guide, but if you are looking to find Hammerburst...
Core Hammerburst Changes
Last week, we announced that the Hammerburst would be removed as a loadout weapon beginning with this Update. This change is being made to preserve its impactful role as a potent long-range rifle but removing the issue with its over-effectiveness when used by a team of players.
The Hammerburst will now be available as a secondary weapon pickup in Core, much like the Markza, Boltok, Overkill and Retro. Here’s the full list of the maps that will now include Hammerburst pickups along with any weapons they rotate with per round (ordered from first to second).
Avalanche – Boltok / Hammerburst
Blood Drive – Boltok / Hammerburst
Clocktower – Hammerburst replaces Smoke Grenade spawn up top
Diner – Shock Grenade / Hammerburst
Dry Dock – Hammerburst / Boltok
Glory – Shock Grenade / Hammerburst
Gridlock – Hammerburst / Boltok
Harbor – Hammerburst / Boltok
Hotel – Boltok / Hammerburst
Impact Dark – Boltok / Hammerburst
Lift – Hammerburst / Overkill
Mercy – Boltok / Hammerburst
Old Town – Hammerburst / Boltok
Relic – Markza / Hammerbursthttps://gearsofwar.com/en-us/community/whatsup-mar1-2018
How to prove your mastery with the hammerburst ?
"Get 10 kills or assists with the hammerburst".
In a single match ; 20 times..
The hardest part of this achievement is to find the hammerburst, that's why I have posted more information about localisation than how to do it :)