Eugene Rakow, 58, of St. Bonifacius told the Minneapolis Star Tribune he was working on a deck Friday when he fired the 3 1/2-inch nail into his chest.
"I was leaning against a board with the gun," Rakow said. "I had the gun at an angle, chest level, and it jumped and I still had my hand on the trigger. It impaled the nail in my chest."
He said it didn't hurt "that bad" at first.
"I could feel it gurgle a little, crunch a little. I knew it wasn't good," he said.
Rakow said he ran to his truck and called his wife. He was taken to a hospital in Waconia and then transferred to one in Minneapolis.
"The surgeon said most people die right there," he said. "He said nine out of 10 won't make it."
It turns out the nail came within 2 millimeters of a coronary artery, Abbott Northwestern Hospital spokeswoman Gloria O'Connell said.
The surgeon, Dr. Louis B. Louis, confirmed it was a close call.
"This nail went through the front and the back of his heart, barely missing critical structures," Louis said.
Rakow got to keep the nail as a souvenir and will be out of work for several months while he recovers.