American Eagle is decent ammo. As has been said, it happens from time to time. Nastiest malfunction for me was a round that kind of went POOF. I was shooting a match, and darn near pulled the trigger again before I could stop myself, RO started hollering about the same time I realized I needed to stop. The bullet had cleared the barrel, in fact someone found it about five feet in front of me, but the barrel was full of what looked like soaking wet powder. Don't know if all that crap would have been enough of an obstruction or not, but glad I didn't find out. Can't remember what brand that was.
Also seen even premium ammo messed up, like a Hydra-Shok (the latest and greatest at the time) that had a crushed and mishapen bullet.
I've had a few cases spit like that with factory ammo.
I wouldn't be afraid to buy Amerian Eagle. Have always found it to be decent. I have seen splits like that in .40 S&W with Remington UMC brass. If you get anymore that split like that out of the same lot, make a special note of it if your collecting them to reload.