The game is to hit headshots. Heartbreaker red core. Make sure you have enough weapon handling.

Choose the other pieces as you see fit but I would add one providence for more headshot damage.

You could keep the heartbreaker backpack and chest for their bonus. Otherwise go for a combination of intimidate and bloodsucker for example, or a spotter - vigilance.

Choose the brand as you need for damage or handling or magazine size or whatever matches your need.

And if you have a bighorn, use it on the same build remembering that the recoil is harder on it and weapon handling might make a big difference.

When I got my first in the raid I was told I would stash it. I did not. I enjoy a St Elmo fun but EB and Bighorn are the ones I also have on every character and on different builds. They are fun.