"I love art," says Hammer, sending up a puff of smoke. "I used to have a painting of Gorbachev that was given to my family by Gorbachev."

None of this is matter-of-fact. Hammer knows most family lore doesn't involve multiple instances of Kremlin-schmoozing. "Hoover hated my great-grandfather," Hammer says. "He referred to him as a Soviet agent of influence." Ironically, the younger Armand Hammer is cast in J. Edgar as Clyde Tolson, Hoover's right-hand man, confidant of five decades, and lover. The movie is no Brokeback Mountain on the Potomac, but it does deal with a complicated and high-stakes attraction between two men charged with keeping secrets for a living. When he was initially offered the part, Hammer balked. "It wasn't the gay aspect I had a hard time with," he says. "When I first read the script, it didn't make sense why Clyde would stay around—because 99 percent of the time he's just taking abuse. But then it was explained to me: When you get that little glimmer of hope—like Tolson did—that simple kiss on the forehead, it all seems worth it and you stay.

"Tolson was the only man who treated Hoover like a human," Hammer says, finishing off his cigar. "They had lunch together every day and dinner together every night. Without exception, never missed it."

In Eastwood's estimation, Hammer delivers "a sleeper performance" worthy of attention and acclaim." Armie's like a throwback to that era," he says. "When Hoover started the bureau, he was 22. At 22, I don't think I knew anything. But Armie's more like those guys, with that ambition and maturity. He's very young but already a full-blown man."

A full-blown man with a firecracker of a wife. Hammer tells the story of how he and the 28-year-old Texas-born TV journalist Elizabeth Chambers once unwittingly exchanged guns for Christmas. "I gave her this little .22 revolver," he says. "She got me a Sig Sauer P220—a great .45 automatic."

It's Saturday night and we're drinking on the back patio at Le Bremner, a packed new restaurant in Old Montreal. Hammer is wearing shorts, flip-flops again, and a dress shirt he accidentally threw in the spin cycle, making it a dress shirt no longer. After dinner, Chambers, in espadrilles, short lacy shorts, and a white blazer, joins us with her father, Bill. "He's a real cowboy," Hammer says. "Do you want to punch him in the stomach? You should feel his abs. I'm not even joking."

He watches admiringly as Chambers describes how she sassed DiCaprio during the filming of J. Edgar. "I actually met Leo when I was modeling in Tokyo when I was in high school," she says. "He hooked up with my roommate. When I saw him on set after all those years, I said, 'Tell me you're not an asshole. Do not make me hate you for the rest of the shoot. She was Spanish—you took a bath your first night together. What's her name?' And he goes, 'Marta.'"

This wasn't just his wife being cheeky, Hammer assures me. "Texas women are incredible. They're like, 'I love you, I'm sweet, I'm kind, but don't fuck with me, because I'll stab you.'" The two met in 2006, at a West Hollywood gas station. Chambers had a boyfriend at the time, and for the next couple of years—until Hammer told her, on the night of the first presidential debate in 2008, to get rid of him. He had prepared a speech over the course of a string of sleepless nights, and it worked. They married in May 2010.

Hammer's eyes brighten as he describes his bachelor party, a 10-day affair he calls his ATF weekend. Starting in Dallas, then road-tripping nearly 1,000 miles around the state, Hammer and his gang of six chugged beer and tracked wildebeests. The culmination of the event was a giant bonfire. "We spent a couple days gathering brush, chopping down trees, building this huge thing, and soaking it with gasoline. We filled a giant tequila bottle with gasoline, too, and put it right on top of the pile. Then I stood back. A long way off. And I blew the thing up with a machine gun."

Chambers says her husband's best quality is his lack of ego, which is evident as Hammer reflexively shifts from talking about himself to telling me about the missus. "Elizabeth broke out of Japanese jail twice in Tokyo while trying to report a piece," he says. "It was two weeks before our wedding. That's my favorite story."