Jamie Gray, wife of Staff Sgt. Henry Gray of the Army Marksmanship Unit, broke the Olympic record for the 50-meter three-position rifle event Saturday, earning the third gold medal for U.S. shooters at the London games. Gray’s score of 691.9 bested the old mark of 690.3, set four years ago in Bejing by China’s Du Li. The American’s qualifying-round score of 592 also set an Olympic record, according to this USA Today report. Gray follows two U.S. skeet shooters to the top of the 2012 Olympic podium: Army Sgt. Vincent Hancock broke his own final and qualification records Tuesday in…