I'm not interested in a standoff with the government. If it ever gets to that point, I've already lost because in their mind, they have a reason to justify deadly force and they will win. Surrender or shoot it out, either way, I lose.
That said, I started buying and storing ammo in the early 1960s. Most of that was GI surplus .45ACP and 30.06 bought at government auctions. Later it was Lake City and a lot of .308. Then came 9MM. In the 1970s I also started buying .22LR in manufacturer direct quantities to get the cheapest price. I also started stashing a lot of Super Vel in .357 and in 45 ACP and .44 magnum. Later it was Black Talons and other specialty ammo, including some amazing black box packed in foam ammo that is no longer manufactured. I made several pallet buys of Federal Hydro Shoks to get a price in .45 ACP and 9MM in the '90s.
I also have considerable amounts of handgun and rifle calibers to go with the various guns I own and shoot for fun rather than defense practice. Most of the shotgun shells are paper rather than plastic. And yes, that WWII ammo still works reliability with only a need to clean the guns more carefully afterwards.
Due to a revived interest in trap shooting, I am now buying pallets of 12 gauge shells when I can get the price I want.
Do I have more ammo than I and my wife will ever shoot? Absolutely. But I also could sell most of it for 20 times what I paid for it, so it is sort of a retirement fund as well as retirement fun.