I'm Nihei, in charge of electric guitars!
Around 1971, Fender revised the design of its Stratocaster and Telecaster models to allow for truss rod adjustment from the headstock side.
Prior to that, the truss rod was adjusted from the neck end, and a nut with a cross-shaped groove (commonly known as a Phillips Head) was used. However, when the mechanism was changed to allow adjustment from the headstock, a new part called the “Bullet Nut” was introduced!!
By turning this, you can adjust the truss rod from the headstock side!
I call it a “Bullet Nut,” but some people refer to it as a “Bullet” or a “Billet,” among other names.
So I asked Google Translate, and it seemed like “Bullet Nut” was the closest match!
As for why it’s called “Bullet,” I think you’ll understand if you take a look at the picture!
Doesn’t it look a bit—or actually quite a lot—like a bullet?
Plus, there are actually different types of these “Bullet Nuts”!!
It might be hard to tell, but one has an angle near the tip, while the other has a smooth curve all the way to the tip!
By the way, just because there’s a difference here doesn’t mean there’s a difference in the hex wrench you use or in how they function, lol.
I hope this was helpful!
See you next time!
Nihei