I ship ammo thru UPS occasionally and have found them the only reliable way to do so in my area. There must be others in the LA Slurb, but I haven't found them. The people at the UPS Customer Service Center which I use are well up on shipping arms and ammo, including all the CA-specific issues.

UPS's contractors ("UPS Stores") are worse than useless--any mention of guns or ammo in our local one has the kid's hand hovering over the 911 speed dial....