[headhunter]

Blowdart Blaster (Nerf)

Not to be confused with the 2016 Zombie Strike Blowdart Blaster. The Blowdart Blaster is a Nerf-branded Perpetual Play Group blaster that was released in 2017. It comes packaged with three Elite Darts. The Blowdart Blaster is a blowgun-style blaster very similar to the 2016 Zombie Strike...

nerf.fandom.com

So technically under California law, Nerf is illegal. Let me explain, to understand you must first read the law which is as follows:
PENAL CODE
SECTION 12580-12582
12580. "Blowgun," as used in this article, means a hollow tube
designed and intended to be used as a tube through which a dart is
propelled by the force of the breath of the user.
12581. "Blowgun ammunition," as used in this article, means a dart
designed and intended for use in a blowgun.
12582. Any person who knowingly manufactures, sells, offers for
sale, possesses, or uses a blowgun or blowgun ammunition in this
state is guilty of a misdemeanor.

Nerf specifically calls their foam ammunition "Darts" so by the definition provided in section 12580 the Nerf blowgun and it's respective ammunition fall into the same category as your 5' .625 big bore with razor darts.
Now let's go on to section 12582, to summarize it's illegal to deal in blowguns AND THEIR AMMUNITION. Due to the fact that the nerf blowgun uses their standard foam darts, those also fall into this category.
Therefor, all standard foam Nerf darts are blowgun ammunition, and are therefor illegal in the "great" state of California.