Oh man not this again! I thought this had been sorted? I haven't found any split cases yet but have had a few Hornadays fail to fire despite a good strike on the case.
Have you inspected the cases with a magnifying lens? The cracks can be very hard to spot with the naked eye, though it gets easier once you know what you're looking for.
I write the above with a mild sense of "what the ****?" because it seems surreal to be giving advice on how to deal with faulty factory ammunition in 2013.
I really think there's precious little point in returning defective HMR ammo to gun shops or distributors compared to offloading it onto the HSE as per the OP.

