Howell birdied seven his first nine holes and added a birdie on No. 7 at rain-softened TPC Deere Run. The two-time PGA Tour winner lost a playoff to Kyle Stanley two weeks ago in the Quicken Loans National.
Schniederjans birdied five of his last eight holes in his lowest round of the PGA Tour. He earned a PGA Tour card last year through the Web.com Tour.
Defending champion Ryan Moore had a 74 in his return from a strained tendon in his left shoulder that sidelined him for five weeks.
The British Open is holding one spot for the leading player among the top five who is not already exempt next week at Royal Birkdale.