The 43-year-old birdied seven holes to card a seven-under 64 at the end of the second round at TPC Twin Cities. Piercy currently finds himself on 13 under par.
After missing four of the last six cuts, the player revealed his confidence is once again beginning to grow.
"It's been a little bit since I've played like I feel like I should play," said Piercy. "To kind of prove it to myself again, I know it's in there, it's just like, okay, how do we get it out of me.
"There's a lot of business to take care of this weekend, but to come out the first two days and do what I did gives me a lot of confidence going into the weekend."
"I've been out here a long time, I know what I need to do," he added. "Just wishing I'd have done it earlier in the season."
Piercy is currently ahead of Argentina's Emiliano Grillo and England's Callum Tarren who, after a round of six-under 65 and eight-under 63, find themselves on -10 and -8 respectively.
Tarren, who was a stroke off the 3M Open tournament record, said: "I hit every green today, so I had so many chances.
"I actually missed probably four or five inside 10 feet, so it could have been ridiculous."
Defending champion Cameron Champ only just made the cut on a round of three-under 68.