California ranges often require bullets to pass the 'magnet test'. This is done in the interest of not tearing up steel backstops in interior ranges with steel cored ammo.
That means that when a RO tests your ammo, it can't stick to a magnet. Of course, the RO is typically not educated in the finer nuances of steel jacketed vs. steel core ammo and they are often lazy when checking too. If the magnet sticks, it can't be used, end of story. It doesn't matter if the magnet sticks to a steel case that is ejected out the side of the weapon and never goes anywhere near the backstop, the magnet stuck, end of story. Even when the RO is smart/thorough enough not to try and stick the magnet to the case and only to the bullet itself, most of the Brown Bears, Wolf, Golden Tiger utilize steel jacketed lead core bullets, which the magnet will of course stick to, end of story. It doesn't matter that 95% of the bullet weight is in the lead core and the jacket is typical stripped off when impacting anything substantial, the magnet stuck, end of story.
Yugo M67 is actually highly sought after because it satisfies the CA magnet test in all aspects, yet is still Berdan primed surplus ammo at an attractive price.