I've had charge backs filed against me, and the buyer got a refund. However, I didn't lose any money at all.
I was covered by PayPal seller protection. I shipped within 1 day of payment, had tracking and sig conf (if over $250), and the DC# showed the item was delivered within 7 days. I got my full refund back.
This has happened to me twice, both times I had to issue a refund to the buyer. But both times PayPal covered my a** once they reviewed the DC# information. You might have to call them to get your refund back, push them a little.