In an interview with Parade, the actor recalled his approach to playing former SAS man Spike, who is tasked with stopping a brutal assassin.
Owen said of befriending the real life officers: "Quite a few of them got into private security and I just happened to get to know them. They weren't necessarily my security, but other people's, and I kind of became friends with them.
"What you notice about all of these guys is that they are much more low-key than you think. They don't strut around. The more serious they are, the less they have to put themselves out there. It's not about showing up and acting stuff. It's much more serious than that."
Owen went on to say that he took the advice he received from the men to heart when filming, adding: "I was playing somebody who had some fury and resentment and anger. He couldn't do [his job] anymore and it was the only thing he knew.
"It was a character who wished he could go out there again and really let himself go."
Watch an extended fight scene with Owen and co-star Jason Statham from Killer Elite below: