Even if “American Sniper” missed out on Golden Globe nominations, it still emerged as one of the big winners of the holiday season. Clint Eastwood’s drama about Navy SEAL Chris Kyle has grossed a stellar $2.2 million since it opened in only four theaters on Christmas, and the Warner Bros. release expands on Jan. 16.

The Oscar lead actor race is especially overcrowded this year, but as ballots are due on Thursday, voters should take a look — if they haven’t already — at Bradley Cooper’s career-best performance. It’s a transformation that had Kyle’s widow, Taya, in tears the first time she saw the film, and she’s been talking about how Cooper captured her husband’s essence. In the last few weeks, many actors, including Ben Affleck, Jane Fonda, Julia Roberts and Jonah Hill, have also been singing Cooper’s praises.

To play Kyle, Cooper spent six months working out 4.5 hours a day, but the role went beyond the physical. He practiced a Texas drawl with a dialect coach, learned how to shoot three military sniper rifles and spent time with Kyle’s family and friends, who gave him access to his emails and home videos.

Cooper, who turns 40 on Monday, had a strong 2014. He picked up a second consecutive Oscar nomination for “American Hustle,” performed the voice of Rocket Raccoon in “The Guardians of the Galaxy” and is now on Broadway in “The Elephant Man.” He spoke to Variety over the weekend.

“American Sniper” is doing really well in only four theaters. Are you surprised by the film’s success?
I’m always surprised when things do well, because you can never bank on that. We were just hoping that awareness was going to be enough for people to see it on Christmas. It was such a competitive market that day — with “Into the Woods,” “Unbroken” and “The Hobbit.” We were happy that people came out in droves for “American Sniper.” And then the A-plus Cinemascore. I didn’t even know they had that.

Actors have been reaching out to you.
I’ve got to say that’s been the most amazing thing. I just heard from Ed Helms and Jonah Hill. I don’t know Ashton Kutcher that well, but he made the effort to contact me to say how he felt about the work and the movie. I’ve never experienced anything like that. It really does make me feel like we’re a community and we’re all invested in each other’s work.

You recently screened “American Sniper” at Fort Hamilton military base. What was that like?
We showed it to veterans. A few years ago, I had the opportunity to take “Silver Linings Playbook” to Walter Reed (National Military Medical Center). Without us even realizing it, Pat Solatano was a character that many young males and women could relate to coming back from war. It was a really impactful film at Walter Reed. That was probably the best experience I’d ever had showing that movie. And so, when we were making “Sniper,” I thought if I could make a movie that people could relate to in this field, I imagined showing it at Walter Reed, which we’re going to do on Jan. 13. We are also going to take it to San Antonio, a hospital there, with Chris’ father and brother. That’s when you really get to experience storytelling and the impact that it could have.

There have been a handful of movies about the Iraq War, including “The Hurt Locker.” Why did you sign on to produce Chris’ story?
I love the character study. Growing up, “Unforgiven” was one of my favorite films, dealing with the psychology of that character. Jason Hall came with me with this story. I saw it right away as a war movie but told as a Western. But everything changed when Chris died and Steven Spielberg came in and said, “We need to make this movie now.” That’s when I fell in love with the guy. It was an incredible experience — the investigative process of trying to get inside a human being’s mind and emotions.

Did you and Clint Eastwood talk about framing it as a Western?
Oh yeah. I constantly talked about “Unforgiven.” When Chris says to his son, “It’s a heck of a thing to stop a beating heart,” it was really right out of “Unforgiven,” when Will Munny says, “It’s a hell of a thing, killing a man.” At the end of “Unforgiven,” when he goes down to get his friend Ned, there’s this storm outside. In terms of Chris’ last tour, we did this desert storm. He’s almost Will Munny 20 years prior to “Unforgiven.”

How much time do you spend in the gym preparing for the role?
In the actual gym? Probably 4.5 hours a day.

Was it similar to your workout for “The A-Team”?
That was totally different. That was cardiovascular and high reps for bodybuilding. This was weightlifting. There was no cardio. There was no toning of muscles. It was just get f–ing strong as a motherf–er.

And when you see yourself onscreen?
My main thing, after each take, the only thing I would ask anybody, “Hey man, am I too big?” When I watched the first cut of the film, I was so monstrous, I thought any more pounds, it would have been farcical.

Did you feel like you got it right as you were shooting?
I knew it was working. I felt him. I felt like I had successfully entered the world of his, so I would be able to tell the story. If you do all the research, you let yourself be open. I had hours and hours of home videos, and all of their email exchanges, and even his workout playlist. I basically had a dossier on this man’s life. And I had his children, his parents, his wife and the people who knew him. It was a huge amount of information to be digested. Once that all happened, and then I got to the size, and I felt comfortable in his voice, or my voice as him, and I got comfortable with the three sniper rifles that he used, then it was like, “OK, let’s tell the story.”

What did you learn from the emails?
Just how fiery their relationship was — how much love there was, how much lust there was. And how much their relationship is relatable. How I could relate to it, and I think anybody who could read them could relate to it. It just humanized him in a huge way.

Your first producing credit was on 2011’s “Limitless.” Why did you decide to go down that path?
I started way before. It was when I was doing “Alias.” I used to get everybody’s dailies. They were video cassettes. I would get back to my little apartment that I was renting, a bottom floor of this woman’s house in West Hollywood, and I would watch them all day long, and then I would go into the editing room. I would only work three days a week, and I was from the East Coast, and I was going to shoot myself living in L.A. I was just so fascinated by the process of making this show. I did that for a year, basically. It was like going to school. Then I went to “The Midnight Meat Train,” with Ryuhei Kitamura, and was very collaborative in the editing room with him. Todd Phillips was like that too with “The Hangover.” By the time we got to “Limitless,” Ryan Kavanaugh at Relativity encouraged me to be part of it in the post-production process, and I became an executive producer. If a director is open to me helping him or her tell the story, I’ll be there as much as they want. I’m lucky that David O. Russell enveloped me with both arms and made me his partner. And Clint was the same way.

How did your career change after your first Oscar nomination for “Silver Linings Playbook”?
You could probably tell me more than I could. I can’t tell you how many times people came up to me after “Sniper,” and said, “Hey man, I didn’t know you could act.” I can’t concern myself with that, or I’ll go crazy.

You’re now starring in “Elephant Man” on Broadway. How do you feel about your career as you’re about to turn 40?
I’m the most fulfilled I’ve ever been artistically. Nathan Lane has got it all figured it out. This lifestyle of doing it, being able to show up and tell a story to 740 strangers every day and sometimes twice a day, and you have the rest of your day free. It’s ideal, and in New York, it’s absolute heaven.

Will you do another Broadway play?
I have to finish this one first. And then I think we’re going to take it to London for three months this summer. I’ll spend half the year doing theater.

Are you going to do a “Guardians of the Galaxy” sequel?
Hell yeah, if they’ll have me.