You must have a dual weapon as primary out, then have a turret (must be a chain-gun for this to work) with a dual weapon next to it.

Press LB and RB at the same time, so that when you pick up the turret, it would be aiming upwards.

You then have the ability to use an equipment (bubble shield, shield regenerator, power drain, and etc. pressing X to use as normal) while holding a turret.

This is very effective while in battle.