Hackney, the Welsh Open champion from Stoke, leads the field - one stroke ahead of Sweden's Maria Hjorth while defending champion Laura Davies trails on 72.
"It is the third time this year I have had eight birdies in a round. I am enjoying it and just hope that it lasts," said Hackney, who was only an inch away from a hole-in-one at the short second hole.
At the same hole Davies needed two attempts to escape from a green-side bunker to run up a double-bogey five before completing her round with late birdies at the last two holes.
"That double-bogey was a real setback," said Davies. "I played well enough and had one or two chances in the middle of the round but it was one of those days when nothing happened."Reuse content