Yesterday I go into a gunsop in Brunswick, Me to see what they had. As usual there gun prices were terrible. Before I leave I decide to check out the ammo. I notice they had Prvi Partizan 5.56 which I thought was a little unusual in a gunshop that is tailored mostly for hunters. I then notice that someone had written in pen over the label .223. I ask the lady behind the desk if she knows that there is a difference and she says that she does but they are still interchangeable. Now I know chances are there won't be any problems but there is a reason that box was marked 5.56. What are your thoughts? By the way they wanted $12.00 a box.