Four years ago, AJ Buckley was worried he was going to get typecast as playing nerdy characters. He wanted more and decided to do something about it. Buckley changed his diet, started running in the morning and going to the gym two to three times a day. Today, AJ is 185 pounds and put on around 25 pounds of muscle since playing Adam Ross on “CSI: NY.”

The new and improved Buckley stars alongside David Boreanaz as Sonny Quinn on CBS’s hit military drama “SEAL Team.” Quinn is a deep character who is an exceptionally loyal soldier, but has a checkered past and self-destructive tendencies.

Buckley chatted with CBS Local’s DJ Sixsmith about his career, his dream job on “SEAL Team” and how transforming his body opened up doors to new roles.

DJ Sixsmith: You’ve worked on over 30 feature films and dozens of television shows. How would you describe your career up to this point?

AJ Buckley: I’ve been really lucky in terms of the fact that I’ve never played the same role twice. I’ve been sort of smart in the sense of keeping things diverse as possible. I was on “CSI: NY” and I was on “Supernatural” at the same time. I was playing nerdy characters and I made a decision at the end of “CSI NY” because I was worried I was going to get typecast as a certain character. My favorite character ever is John McClane from “Die Hard.” I always wanted to play these sorts of characters, but physically I wasn’t right. I was up for a pretty big film after “CSI NY” and they said I was the best actor for the job, but physically it’s just not him and we don’t have enough time to physically change him. I said to my wife that I never want that to happen again and I really want to focus on changing how I look in order to open up different doors for more roles. Over the space of four years, I probably put on about 25-30 pounds of muscle. Then the opportunity for “SEAL Team” happened. It was the same casting director of “CSI: NY” and when I walked into the room she was like, ‘what the hell happened to you?’ I was 145 pounds playing Adam Ross on “CSI: NY” and I’m 185 pounds playing Sonny Quinn now.

DS: How did you put on that much muscle?

AB: I hired a nutritionist. Nutrition is the key for me. You can spend hours in the gym, but if you’re not putting the right gas in the car, it’s not going to run properly. I figured out what I can and can’t eat, the timing of when I eat and I made it my full time job when I was between jobs. I got up early, went running, came home for breakfast and went back to the gym again. It was about two to three times a day in the gym for about four years.

DS: What makes “SEAL Team” different from all of the other projects you’ve worked on in the past?

AB: First, it’s a dream role. I mean, we get to fly around, blow things up and shoot guns. I think that the subject matter is all about who we are representing and the importance of how we tell the story. I think it has been really taken into account by our producers and by the cast. The advisors that we have on the show and some of the producers are former SEAL Team and Special Forces guys. It’s a TV show at the end of the day, but we need to be authentic as a network show portraying these guys. We can’t have moments with unrealistic things. We portray these guys in these scenarios that aren’t far fetched and then find these moments in how these guys deal with these insane moments. Then we cut to them coming home, driving their daughter to school or having a conversation with their wife after they’ve been in a gun battle 48 hours prior. That’s not untrue, that’s how these guys do it at this level. When we sit down with these guys, I ask them how did you do that? I have the utmost respect for these guys and even more so for the country I get to live in.

DS: Your character Sonny Quinn is an interesting person. What is the most difficult part of playing that character?

AB: He’s got this bravado about him and a country boy Texas, knock down the doors and kick ass type of thing. I really wanted to have the ability to show his vulnerable side. When I talk with our show runners, I want to know what is behind this bravado in his quiet moments and where is the pain. Some of the guys that I spoke to when researching this character said there is a lot of pain in there. I want to humanize Sonny and show that there are cracks in this big, tough and hard charging guy. As you get to know him, then we go deeper into that pain and what that pain is. These guys don’t talk about it or don’t want to talk about it.

DS: What can viewers expect on tonight’s new episode of the show Pattern of Life?

AB: I love all the episodes, but I think this one stands out for so many reasons. It’s a mission that takes place in real time where we’re given an objective and the second the doors are kicked open at the beginning of the episode, we have 45 minutes to get in, get the intel and get to the exit. Within that 45 minutes, things go wrong. During the filming of the episode, we actually shot it in sequence. For those who don’t know, when you shoot a TV show, it’s all out of order and you don’t know what the order of the show is. This one was shot in order and it required your intensity to be ramped up. This episode is so beautifully shot, the pace is there and the intensity is there. I’m so proud of this particular episode.

SEAL Team” airs Wednesday nights at 9pm EST/PST on CBS.