Gary Hallberg of the United States equalled the course record at a blustery Turnberry to lead the Senior Open Championship by three shots.
The 54-year-old recovered from an early bogey on the Ailsa course to put in a superb burst of eight birdies in 13 holes on his way to a seven-under-par 63.
It left him clear of first-round leader Bernhard Langer and American Tom Lehman. Langer played steady golf in the windy conditions to reach the turn in par and went on to birdie the 11th.
But a disastrous triple-bogey seven at the 13th, followed by another bogey at the 17th saw him slump to a round of 73.
Hallberg carded perhaps his most impressive three of the day at the 14th.
Having missed the green to the right, one of his only errant shots of the day, the man from Illinois holed his 40-foot birdie putt from off the green.
An eighth birdie of the day at the long 17th helped seal a memorable day for the 1980 PGA Tour Rookie of the Year.
"When I was five over on the first day after nine holes I thought, I'm not playing that bad," Hallberg told www.europeantour.com.
"I was playing good but I just couldn't get it going. So I hung in there and played a great back nine; I think the 40 helped me because it turned me around mentally to go play aggressively.
"So I played aggressively today, had some great putts go in but I also missed some putts from around six, seven feet today but you can't make them all.
"It was one of the great days that I've had in many years on the golf course. It was just a pleasure."
Englishman Roger Chapman's bid to become only the second man after Gary Player to complete a senior major grand slam following his triumphs in the Senior US PGA and Senior US Open championships ended in disappointment after he failed to start the second round because of a neck injury.
"I'm just so disappointed because history beckoned and I would love to have equalled Gary Player's record and I felt like I could have done well round here," said the 53-year-old.
Collated second-round scores (Gbr & Irl unless stated, par 70):
134 Gary Hallberg (USA) 71 63
137 Bernhard Langer (Ger) 64 73, Tom Lehman (USA) 66 71
139 Dick Mast (USA) 66 73, Peter Senior (Aus) 68 71, Jay Don Blake (USA) 66 73, David Frost (Rsa) 66 73
140 Michael Allen (USA) 66 74, Mark McNulty 65 75, Peter Fowler (Aus) 68 72, Fred Couples (USA) 72 68
141 John Cook (USA) 69 72, Mark Wiebe (USA) 70 71, Mark Brooks (USA) 70 71, Ian Woosnam 71 70, Bobby Clampett (USA) 70 71, Barry Lane 67 74
142 Anthony Gilligan (Aus) 69 73, Mike Goodes (USA) 69 73, Boonchu Ruangkit (Tha) 69 73, David
J Russell 69 73, John Huston (USA) 70 72, Corey Pavin (USA) 70 72, Olin Browne (USA) 69 73, Eduardo Romero (Arg) 68 74
143 Kirk Triplett (USA) 69 74, Carl Mason 69 74, Fred Funk (USA) 69 74, Gary Wolstenholme 70 73, Mark Mouland 71 72, Loren Roberts (USA) 68 75, Chien-Soon Lu (Tpe) 66 77, Anders Forsbrand (Swe) 71 72
144 Mark Calcavecchia (USA) 72 72, Tom Watson (USA) 69 75, Chris Williams (Rsa) 71 73, Ross Drummond 70 74, Philip Jonas (Can) 73 71, David Eger (USA) 74 70
145 Kouki Idoki (Jpn) 69 76, Marc Farry (Fra) 71 74, Phil Hinton 70 75, Rossouw Loubser (Rsa) 74 71, Lee Rinker (USA) 67 78, Tim Thelen (USA) 73 72, Jeff Freeman (USA) 71 74, Jeff Hart (USA) 69 76, Kevin Spurgeon 72 73, Des Smyth 75 70, Paul Wesselingh 69 76, Larry Mize (USA) 71 74, Philip Golding 70 75
146 Rod Spittle (Can) 72 74, Steve Pate (USA) 71 75, Chip Lutz (USA) 70 76, Joel Edwards (USA) 69 77, Jeff Sluman (USA) 70 76, Angel Franco (Par) 73 73, John Ross (USA) 75 71, Bob Gilder (USA) 72 74
147 Juan Quiros (Spa) 71 76, Mitch Adcock (USA) 73 74, Seiki Okuda (Jpn) 73 74, Tom Kite (USA) 74 73, John Harrison 73 74, Tim Elliott (Aus) 71 76, Andrew Murray 69 78, Jay Haas (USA) 73 74, David Merriman (Aus) 70 77
148 Mike San Filippo (USA) 72 76, Randy Haag (USA) 74 74, Denis O'Sullivan 76 72, Mark James 74 74, Noel Ratcliffe (Aus) 72 76, Mike Cunning (USA) 73 75, Bill Longmuir 71 77
------------------------------The following players failed to make the cut----------------------------
149 Tony Johnstone 67 82, Andrew Sherborne 71 78, Tom Eubank (USA) 77 72, Bob Tway (USA) 69 80, Andrew Magee (USA) 71 78, Sam Torrance 73 76, Peter Mitchell 74 75, Gordon J Brand 72 77, Andrew Oldcorn 72 77, Miguel Angel Martin (Spa) 74 75, Philip Walton 73 76, Gordon Brand Jnr 75 74, Greg Norman (USA) 72 77, Yutaka Hagawa 73 76
150 Craig Stadler (USA) 70 80, Bobby Lincoln (Rsa) 73 77, Eamonn Darcy 76 74, Jim Rutledge (Can) 72 78, Steve Jones (USA) 74 76, Brad Faxon (USA) 71 79, Chip Beck (USA) 69 81, Sandy Lyle 72 78
151 Rick Gibson (Can) 70 81, Gerry Norquist (USA) 71 80, Stan Utley (USA) 72 79, Glenn Ralph 75 76, Mike Harwood (Aus) 74 77, Richard Fish 76 75, Kevin Phillips 78 73
152 Peter a Smith 72 80, Stephen East 72 80, Stephen Mcallister 75 77, Jean-Pierre Sallat (Fra) 71 81, J d Kim (Kor) 74 78, Jose Rivero (Spa) 79 73, Roger Roper 72 80, Angel Fernandez (Chi) 74 78, Isao Aoki (Jpn) 73 79
153 Bruce Vaughan (USA) 76 77, Mark McCumber (USA) 75 78, Costantino Rocca (Ita) 76 77, Fred Wadsworth (Ger) 73 80, Darren Cole (Aus) 78 75, Danny Edwards (USA) 72 81, Malcolm MacKenzie 72 81, Tommy Armour III (USA) 70 83
154 Richard Masters 75 79, Rodger Davis (Aus) 77 77
155 Darrell Kestner (USA) 73 82, Alastair Webster 77 78, Bob Cameron 78 77, Jose Buendia (Spa) 76 79, Steve Cipa 76 79
156 Pete Oakley (USA) 73 83
157 Stephen Mcnally 77 80, Graham Banister (USA) 70 87, Charles Bolling (USA) 77 80, Campbell Elliot 77 80, Wayne Grady (Aus) 77 80
158 Wayne Westner (Rsa) 73 85
159 Dave Wettlaufer (Can) 76 83, Joe Daley (USA) 78 81
160 Nick Job 79 81, Noboru Sugai (Jpn) 79 81
161 Richard Kaplan (Rsa) 74 87
163 Tony Jacklin 80 83
167 Barrie Stevens 79 88
WD: 72 Roger Chapman
