I'm saving up for some primo ancient Armor, and need a ton of ancient gears, shafts, and cores to get it. It seems like the gears and shafts are fairly regular drops, and sometimes can be found in rusted-out Guardians without a fight, as well as in a pile from defeated large and small Guardians.
But I'm having a lot more trouble locating cores. I think the only ones I've gotten so far came from defeated full-size Guardians, but now I can't recall.
Which (live or dead) Guardians can drop cores, and are there any particularly good ways to find a bunch of em?