Several years ago I experienced the same thing with some of the 'old' Federal Match (Pre-900 series) that was made for Federal by Eley. Had shot more than 15 cases of the stuff with no problem and suddenly 'kaboom' and it cost me an extractor in an Anschutz. Notified Federal and they told me I had a headspace problem. Told them I must have FOUR headspace problems because it ended up doing it in 4 different rifles. At their request, I sent them ruptured cases, good cases, and much of the same lot number. They ran it thru metalurgy and a full battery of tests. It turns out that the ammo had been stored at the distributor in the proximity of a source of ammonia... probably spilled bore cleaner... and that had caused embrittlement of the brass. Federal traded me 5 cases of then-new 900 for 4 cases of suspect 'old' match. What a deal. Check your storage area... then your point of purchase. Don't shoot any more of that lot... extractors are about $38 apiece.
