If you max out the Ammo skill you will rarely get any weapons attachments … for example i played with Friends and we killed like 10-20 of those big big Tanks ( yes i dont know the Name of those 
)and they get a lot of lvl 5 attachments and even weapons … and i “only” get a ton off 5.56 ammo and 50 cal ammo. Or when we lootet those smaller attachments box in High loot zones its mostly the same loot for me : A granade, Landmine, lockpick and sticky Flare while they get lvl 3-5 attachments. They even had so much good attachments they startet droping me those …
If you are connecting to a friends game there is a bug. Ammo boxes are empty or dont’t give as much as for the host. And there is a skill to increase amount of ammo you can loot from robots and one that can give you more parts from them.
Not sure if they check your inventory or even the save itself now, after they added the loot-timer for all static boxes?.
The FNIX (red and black) tanks had a ~100% droprate of 1 golden weapon and 1 golden attachment before it were patched, on the other hand they took so much ammo to kill, that most long time players didn’t even bother to mess with them, as we already had more gold weapons than we could put on our passive inventory chars.
Before that the FNIX harvesters had an average of 1 in 3 droprate for golden weapons and/or attachements, while almost all attachments could be farmed in the northern bunkers (Skvadern and Hermelinen), and it usually gave 2-5 attachments per run in a bunker.
I had the same skills on 2 of my chars since April at least (only one more level/point as they upped from 30 to 31)
All this time, and before it on my first char, I’ve had the first 4 skills in the right tech-tree maxed, as I consider it almost as much of a ‘must have’ as increased inventory.
I have yet to find a single golden weapon from a FNIX Tank or Harvester since the loot-timer were added, and the explosions/pockets got better again.
Yesterday my co-op mate found a gold weapon 8that neither of us wanted or needed), and today I found a gold mag for the AG4 (AK4) from FNIX tanks/harvesters (that weren’t really needed either) but at least they still drop eventually.
So they really have gotten a lot more rare, and I found no random gold weapons in any boxes, just the ones that are already placed out in the world as a ‘once per character’ pickups.
At the same time my co-op mate also have the salvage skill, and he finds stacks of 200+ of ammo, while I never found a single stack of 180+ and are quite used to <50 in boxes, and at times even a single shot!! depending on the region. (1 shot minus 100% extra from salvage skill = well… nothing!)
Personally I’m happier to find 3 stacks of 8 rockets, and a few stacks of 120+ of the ammo I’m using (for the region) from the tanks and the harvesters.
But if one have started a new char, it might feel a bit ‘cheap’, but at least you get XP from it too, so a ‘free kill’.
The best place for golden attachments are still in looting boxes and bunkers in the northern regions of the map. But now you have to wait 4 online hours between the runs, so no matter how you see it it’s a lot harder to get golden stuff now.
Not sure how much of a hit to the loot-table the introduction of the bikes took?
