Another legitimate reason for burying your weapons on your own property you reside, especially in a no-carry state like us, is if you happen to come upon your home in mid-robbery, mid-rape of your wife and/or daughter(s), mid-sodomizing of your 8 year old son and unconscious baby-sitter, mid-vandalizing, mid-vegetarian potluck, etc.
Now, when it comes to caching for governmental gun grab? It's hard as hell on the island, for sure. But, like the guy I talked to did, I'd probably go throw em in the ocean!! We'd have to assume that there will be a lot of digs/metal detecting/satellite/GPR scans in popular places like St. Louis Heights park, Tantalus lookout, Pali Hwy lookouts, other parks, etc. We'd hear on the news about how they're finding all these "domestic terrorist weapon caches" all over the island.
Then on the other hand....we are surrounded by this massive ass ocean in which only a relative few ever visit the sea floor.
Anyone up for a recreational night dive?

I would personally do it closer to shore where no equipment is required, but they'd be looking there too.
Almost forgot
/tinfoilhat