Other thread was closed but I thought I should share my experience with FOC and wrong guns.
I ordered 2 Mossberg 20 gauge shotguns from FOC, got my shipping notification and they were on the way.
Before they arrived FOC emailed me and said they were sorry, the shotguns were actually 12g. Here is a pre paid shipping label. When they arrive, put the label on and send them back and when they arrive we will send you the refund.
So I got the guns, never left the PO, taped the label on and sent them back, got my refund. No drama.
Hopefully this is somewhat relevant to the other thread.