Most banks don't get their coin from the Federal Reserve. They get it from one of the carriers (Brinks, Loomis, Garda, etc.). Typically, they put an order in each week for the coin (and paper money) they need for the week. When you go in and ask to buy a box, it takes that box out of their stock. If they don't keep "extra", then they have trouble supplying change to their business customers.
You asked for half dollars. Some banks are not willing to order half dollars because businesses don't want them, so there's no outlet for them, except those of us that search them. Keep in mind that the bank pays the carrier for delivery and pick up of coin and paper money, so if they order a box of halves for you, that is costing them money and it costs more if they have to return them.
I go through cents, nickels, dimes, and quarters each week. I do that by having a stock of them already and trading boxes. That way the bank's inventory doesn't change. It took a long time to build up to full boxes, but you can do it. Start out by asking to buy a few rolls and work up to a box, then approach them about just trading each time. It likely won't work for halves, but should for other denominations. Be honest about what you are doing and make sure each roll you trade in is accurate. I've been doing this since 1974, when I started with $5 in cents. Honesty and trust are your best friends. Now, the banks I trade with like my rolls because I guarantee they are all counted accurately and I've removed the foreign coins (except some Canadian). The business customers love them because they know they are accurate.
Bringing in candy for the tellers a couple times a year helps, too! Mine love York Peppermint Patties. I get the 175 count box from BJs.
Scott
