That little round "tear" is actually the aftermath of the heat sealing of the crimp common to many factory loaded shells. All of my Winchester shells have that melted depression right in the center of the crimp that looks like they melted the plastic with a hot metal rod (which is probably exactly what they did).

Here is exactly the same Winchester Super-X 00 Buck shell that I removed from my home defense shotgun...

Sorry for the bad pic, my camera doesn't do macro shots very well, but you can see the little round melted seal in the middle of the crimp.

Mike