I wish they had tested 10,000 rounds of Hornady Steel Match.
My rifle had extraction issues with 2 rounds out of the first hundred or so I shot. I also noticed that, if I loaded my P-Mags to the full 30 rounds, simply hitting the bolt release on a full mag wouldn't fully feed. Pulling and releasing the charging handle was necessary. That little extra bit of momentum was needed.
Haven't had any extraction issues since. The 75 gr stuff that I was using shot real nice, too.