Originally Posted by jambo
So can you elaborate ?
when did this go into effect ?
There really is no elaboration. The purchase, sale, and/or possesion of armor piercing ammo is illegal. It has been for some time. There is about a gazillion things that would come up with a simple google query or search here at calguns. At the top of each page here there is an admonition to 'read the rules before posting'. I'm pretty sure that it is mentioned there too. Anyway, since you seem to be asking genuinely, this would cover any/all centerfire rifle ammo and 9mm handgun ammo. I am not certain if other handgun calibers are banned outright as well...or just not available anywhere anyway.
I am going to take a wild stab and guess that you are either just getting into the 'gun thing' or are an out of state .mil stationed down south and may not know all of the intricacies of CA firearms law. Trust me, I am no expert. But I have found a powerful resource here at calguns and encourage you to avail yourself of the same and become a regular here as well.