Seems like they would still take an order even when out of stock, but saw no way to place in "cart".
I don't blame them at all. If they take your order, they are also confirming a price. What if they can't produce and ship for X months, but in the meantime the price of lead and bullet jackets doubles. They can't go back and ask for more money, they have confirmed a price by accepting your order.
By doing it your way, they could spend the next several months shipping product for free (actually, under their cost to manufacture). Which might/could put them out of business.
So given the choice, would you rather
eventually have the opportunity to order your favorite bullets,
or never again have your favorite bullets ??