system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40.000] Could I kill a bunch of Orks with a thrown rock, if I convinced them it was a grenade?

So, they have a sort of psychic field that distorts reality according to what they believe. That's why their rickety garbage technology works: Because they believe it works. They've also, apparently, been known to steal vehicles with no gas in the tank, simply because they believed it was functional.

So if I was facing a whole horde of Orks, could I just shout "Grenade!" while throwing a rock, and it would do something, as long as they heard me?
gpt
No.

Thats not how their Gestalt field works. It kind of does, but not to that extent. Basically, their belief system and warp-capable brains act more like oil in a machine. It *bends* reality, it doesnt outright change and break it.

They can make crude machines run and act like they're supposed to because they still on instinct know *how* to make them work but their belief system just adds that extra bit of spit and shine to their items thats boosts it a bit further. Classic examples of this are the "Red 'uns go fasta'!" thing, or that Blue is lucky or purple is *sneeky*. 

A gun made by an Ork will be a crude jumble of parts but it will still *work*, except in the hands of an Ork it just works *that little extra better*. For example it wont jam as much, it might be more accurate or any other example of mild performance. It wont however suddenly transform a normal slugga into a grenade launcher because someone decided it is. Keep in mind however, that in a freak accident, if a Boy hits the fuel tank of a vehicle and it bursts into a fireball they *might* consider their gun more killy, but it wont be suddenly firing explosive rounds, it'll just be that slightly more probable to hit weak parts of armor, fuel tanks or ammo reserves.

Overall, think of it like Marvel Domino's superpower to affect luck. Things just kind of flow and work better the more Orkz believe in something, but it wont physically alter the material plane to the extent where a box of scrap parts is suddenly a plasma generator or a burnt out, destroyed tank can suddenly repair itself and work again. Your rock is still just a rock. If you're lucky and they believe it to be dangerous, it might just accidentally kill a Grot that was hiding nearby when you threw it.