Bradley Cooper left no stone unturned when he trained for his role in American Sniper. ZOO chats to him about his hardcore trai

What kind of working out did you do for the role?

Chris Kyle [Cooper's character] was 230 pounds of muscle and I was about 185 pounds at the time, so it was three months of constant eating and working out. It was tough.

Tell us about the hardware and training to be a sniper.

I trained with the.338 Lapua, a.300 Win Mag and a MK11, which are the three sniper rifles Chris used, and just becoming comfortable with those weapons was imperative. But there's this other quality, the ability to operate in very high-pressure situations in a way that's extremely methodical.

It's fascinating what you have to know; how to be prone on the gun, how to have your feet in a certain place and even control your breathing. And then there's how long these guys do it. Chris could stay on the gun for eight hours without moving, which is an incredible feat.

How much preparation was there?

I only had three months so I had to choose what to become comfortable with. I really wanted to focus on getting into the mindset of being a sniper. Not so much about the training of becoming a navy seal, but I'd love to have done if I could survive it.

So I supplemented that with the weight training, which pales in comparison with what SEALS do but at least I could understand that kind of focus and sacrifice.

So you became a real shooter with live ammo?

Yes, the guys training me with live ammo in those three weapons made a massive difference.

The first time we were in Morocco shooting the opening scene in the movie [the scene from the trailer], it was my first time behind the scope outside target practice, so I'd only felt the gun with live ammo.

I saw the two actors in the scope and my stomach turned. I couldn't shoot the scene with them there even though the gun wasn't loaded. It gave me a glimpse of what a soldier has to go through.

You produced American Sniper, which means you hired the director, Clint Eastwood. What made him the right director?

It's the most hilarious question I've been asked; why would I want to work with Clint Eastwood?

He's made maybe the best American Film – Unforgiven. The character struggle of a man he tackles in films like Unforgiven and Letters From Iwo Jima, he's just able to do in ways other directors aren't. So he was the perfect director for this movie, which is a character study.

It's also framed as a western, so he's perfect. Chris Kyle actually said if there was any way he had a choice of who'd direct the movie he'd want Clint Eastwood.

How is an Iraq war movie like Unforgiven?

The construct and the way we set it up. There's a sharpshooter, an enemy sharpshooter and a showdown at the end, almost like you're in the frontier with tumbleweeds. When you think about it it's almost got the Sergio Leone/Man With No Name whistle. We even did that in the pitch.

Chris says in the movie 'it's a hell of a thing stopping a beating heart'. William Money in Unforgiven says 'It's a hell of a thing killing a man'.

Is Chris Kyle like William Money?

If you look at Clint's canon about the different stages of the man it's almost that this character is William Money prior to when we meet him in Unforgiven. His wife has since died and he's taking care of their kids. So we saw a lot of similarities.

So how was Eastwood to work with?

Sometimes on a movie you feel like you're warming up on your first three takes, then you'll get into it on take seven and eight. That's not happening in an Eastwood movie at all.

You better bring it on the first take and if he feels like he has it he'll ask how you feel and move on. There weren't many more than one or two takes, often just one. That stuff on the gun was one take almost every time.

Do you prefer lots of takes?

I'm comfortable with few takes after doing two David O Russell [The Silver Linings Playbook, American Hustle] movies. When you step out of the van in the morning on his movies you better be able to shoot the scene the minute your foot touches the ground.

I've actually come to love it because there's an energy and vitality and a sense of it actually happening. If I ever get the chance to direct I think I'd always want to do that. Never make them feel as if they have 100 takes, make them feel like this is it.

Most scenes depicting characters on the phone can be a bit dull. Not here. What was it like to shoot the 'talking dirty' scene?

There was a logistical dilemma. I couldn't figure out with Clint how I'd hold the phone and the gun and not look goofy, so we settled on the earbuds.

Clint had this great idea where I should try and get the volume up because I really want to hear it, and it was so great because there's this moment where he puts the gun down to turn up the phone to make sure he could hear it. I was laughing so hard I couldn't get through it.