Australian duo Nick O&aposHern and Rod Pampling are within four shots of the lead at the halfway point of the AT&T National. O&aposHern shot a stunning round of 65, while Pampling added a 69 to his opening 66 as the duo finished the day in equal fifth position at five-under and just four shots behind American pair Tom Pernice Jr and Jeff Overton. Pernice Jr shot a blistering seven-under-par 63 to grab a share of the clubhouse lead at nine-under, while Overton shot a bogey-free 65. Anthony Kim is in third at six-under after carding his second consecutive 67, while a group of seven players are tied with O&aposHern and Pampling at five-under, including Steve Stricker and John Merrick, who shot 64s and first-round leader Steve Marino, who signed for an even-par 70. Pernice played his first five holes on the Blue Course at Congressional Country Club in even-par before catching fire, starting a string of four straight birdies at the par-four sixth. He added three birdies on the back nine, including one to close his round at the par-four 18th. It marked the second time this year that Pernice shot a 63. He also reached that number in the final round of the St Jude Championship last month en route to tying for eighth. Winless on the PGA Tour since claiming The International in 2001, Pernice missed the cut last week at the Buick Open. Defending champion KJ Choi has fallen eight shots back of the leaders after a one-over 71 dropped him to one-under and a tie for 26th, while Australian veteran Robert Allenby is still in touch at three-under. John Senden, Gavin Coles, Stuart Appleby, Matt Jones, Stephen Leaney and Peter Lonard were the other Australian&aposs to make the cut, while compatriots Jason Day, Brett Rumford and Mathew Goggin were not so lucky. Second Round of The AT & T National (Par 70): -9: Jeff Overton 66 65, Tom Pernice Jr 68 63 -6: Anthony Kim 67 67, Cliff Kresge 69 65 -5: Rod Pampling (Australia) 66 69, Steve Stricker 71 64, Nick O Hern (Australia) 70 65, Steve Marino 65 70, John Merrick 71 64, Jeff Maggert 70 65, Billy Mayfair 67 68 -4: Patrick Sheehan 69 67, Tommy Armour III 67 69 -3: Todd Hamilton 70 67, Robert Allenby (Australia) 68 69, Jose Coceres 69 68, Parker McLachlin 71 66 Also: -1: John Senden (Australia) 70 69 E: Gavin Coles (Australia) 69 71 +1: Stuart Appleby (Australia) 67 74 +2: Matt Jones (Australia) 74 68, Stephen Leaney (Australia) 71 71 +3: Tim Wilkinson (New Zealand) 71 72, Peter Lonard (Australia) 74 69 +5: Jason Day (Australia) 71 74 +6: Brett Rumford (Australia) 73 73 +9: Mathew Goggin (Australia) 73 76