Bulging Biceps - You do not need to brace in order to fire heavy weapons without penalty. Normally doing so inflicts a -30, and semi/full auto are prohibitied. All marines have Bulging Biceps.
Recoil Supression (armour) - This allows basic weapons to be fired one handed without penalty. Normally it is a -20 penalty to do so.
Bring Death From Afar - This ability plays on how the rules for Full Auto work.
Normally, Full Auto is a full round action that allows a Full Auto attack, at a +20 BS. The attacker must stand still for this benefit. There is an option to make a half move as part of the attack, but it causes the attack to be at a penalty (-10 penalty instead of +20 bonus I think, you'll need to check the exact rules for Full Auto Attack).
Bring Death From Afar lifts this penalty, and makes it possible to move and fire with less of a penalty. It is useful as it allows the gunner to advance with the group, instead of forcing issues of squad range being broken up. Its exact wording breaks it up by weapon type.
Pistols only have to bother with Bring Death From Afar.
Basic Weapons need to check the interaction of Bring Death From Afar + Full Auto Attack. Also note that it can be fired one handed without penalty. For the sake of your GM, please do not dual wield. Its silly.
Heavy Weapons - You can move and fire without bracing, and will need to read how Bring Death From Afar modifies the bonus for heavy weapons while moving.
Ultimately, Bring Death From Afar does one thing: It modifies the penalty one suffers when using the Full Auto + move action.
Also, one other item that does indeed interact is Suspensors, the weapon upgrade. This turns Full Auto into a half action. Technically, it stacks, as it allows the firer to Half Move + Shoot/Half move for effectively a no-penalty Full Auto attack and Full move in the same turn.