Lundberg and Sandelin are at 13-under 131 for 36 holes. They have a 1-stroke lead on Robert Rock, who also shot 64 Friday.
The four golfers who were tied of the lead after shooting 65s Thursday saw their scores balloon. Joakim Backstrom, David Carter and Roope Kakko each had 73s Friday and are seven strokes off the pace. Fredrick Henge shot 77 and is 11 strokes back.
Lundberg started his round with a birdie and a eagle but then had bogeys on both 3 and 4. He still made the turn at 3-under and had four birdies in five holes on his second nine in climbing the leader board. He added a birdie at No. 17 for a closing nine of 31.
Sandelin opened play on the back nine and was also 31 for the first half of his round. He bogeyed No. 1 -- his 10th hole -- and answered with a birdie at No. 2 and strung together three birdies at Nos. 6-8 for his 64.