Charlie Hunnam talks ‘Triple Frontier’ and how he stays grounded in Hollywood. — In J.C. Chandor’s “Triple Frontier,” Santiago “Pope” Garcia (Oscar Isaac) calls upon the best of retired Special Forces Ops to pull off a risky heist in an unspecified multi-border zone in South America. The men — played by Ben Affleck, Charlie Hunnam, Garrett Hedlund, and Pedro Pascal — leave their tattered lives behind for a dangerous mission — the takedown of a drug cartel boss. Their “reward” is walking away with his loot, but they soon discover it all comes at a price.

We recently caught up with Hunnam, who plays William “Ironhead” Miller in the movie. The 38-year-old Brit, best known for his role as Jax in FX series “Sons of Anarchy,” talks about how he prepared for the heist film and how he stays grounded in Hollywood.

The film tackles the psychological impact of a career in the military. Is that something you researched before filming?

It was my intuition before I even read the script. That’s what interested me about this world. It’s the two fundamental aspects very specifically attributed to the experience of being a soldier that is not very well talked about. I mean PTSD is a hot topic but there’s an umbrella of PTSD, which is really just about purpose. What do you do when you have dedicated your life to a certain skill set and through that belonging to a really deep sense of community … What do you do when all of that basically gets taken away from you? When you come back and you don’t have a deep sense of community anymore? The primary skill set that makes you feel vital is no longer deemed valuable and yet you’re still in the prime of your life. It seems to me like a really, really difficult dual aspect of reintegration that has to be dealt with.

This is also very a physical film. There’s a lot of traveling and hiking with all of that bulk through strenuous conditions. How much of that did you really have to endure?

It’s become this sort of fashionable and very common narrative that seems to have developed in the filmmaking community where they like to talk about how difficult it is to make these movies. Maybe it’s sort of an unapologetic aim to make themselves sound heroic. My perspective is that the physical challenges of making films are never that difficult. Where the real challenges lie is getting the work right. It’s the creative challenges, the emotional, intellectual, spiritual challenge of trying to [do] a very important subject matter of justice.

At the same time, there also has to be a little physical prep for filming those certain sequences. Do you adhere to a physical regimen before shooting?

It’s a necessity for me to stay in shape. It’s one of the elements of my day to day therapy. I like to stay fit and eat healthy. For this, I had just done a project that I’ve lost a lot of weight for and J.C. wanted me to be as formidable as I could be. So, I just got back to the routine of eating very, very heavily and protein-rich and lifting heavy weights. Garrett was taking the physical elements of this job very, very seriously too. And he’s been a lifelong buddy of mine. So, I got to go train with him a lot and, keep him company in the gym.

What keeps you grounded despite the success you’ve had in your career?

I think probably the terror that it might run out at any point and then I would be confronted with the issue that we deal with in this film, which is how would I continue to feel valuable in my life? I feel like the vast majority of people who work in this business live in constant terror that may be their run of good luck or ability to keep making a living at this will potentially run out at some point. In terms of staying grounded, just be a normal person. I think where I’ve seen a trend of people becoming affected by success is that they got into this for extrinsic reasons rather than intrinsic reasons. People who got into this wanting fame and wealth as opposed to people that felt that storytelling would be a really judicious use of their time.