No idea about age of ammo, is there somewhere on the box to find out? Some of the shells do have slight discoloration (very small brown patches), but I've noticed this on other centerfire Winchester rounds I get. (.243, mainly).
I've put 7 rounds through it; didn't notice the split one until after I got home. It goes up and down the case, not across it for the record.

Ben - so far I'm enjoying the step up! Though Mr Right Shoulder isn't so much. I'll be the wimp who blames "that hard factory rubber pad" though

Cheers
Troy