Ok, so you know the drone, the one the engineer uses, the one that's a pain but also deals a ton of damage when you stack the core by using an item. Well, today, were going to break that stack and turn engineer into the run-and-gun powerhouse that he is.
First, we need one item, the item that will break the core stack. That item happens to be one of the least sought-after items in the game, the Powershot. See, the Powershot, unlike other passive items, has no cooldown, instead, it activates every six shots. This means that every six shots, it bumps the core stack up by one.
The Engineer generally works well with an SMG, usually ones that generate a lot of heat and have a fairly large mag and high firerate. This type of weapon also happens to be perfect for bumping up the core stacks.
Now, about getting that item. Synthetik's random generation makes nothing certain, however, playing on a high difficulty modifier to maximize the amount of chests you find will certainly help. For those who are dead set on the build, equip transmutate and any starting item, then recycle the item, and you have a decent chance of getting a Powershot.
Have fun with this...