The Martial Art used in this movie is Pencak Silat, the indigenous fighting style of Indonesia.
Every actor who played a member of the SWAT team went through a training program with KOPASKA (Indonesian Navy's Special Ops) to study the techniques used in the force including weapons use and hand signals.
Gareth Evans originally wanted an action drama set in a prison. When the approved budget was too small, he pared it down to a one-building action film that became The Raid. The success of this film allowed him to secure a larger budget for the sequel where he got his wish of a prison drama.
Yayan Ruhian (Mad Dog) had once trained Pencak Silat for Pasukan Pengamanan Presiden (the Indonesian Presidential Security Forces- equivalent to US Secret Service) in 1989 and for the Indonesian Military Police Corps in the early 1990s.
All the guns used in the film are Airsoft replicas and not functioning firearms. All the shots of the guns actions cycling, muzzle flashes and casings ejecting were added digitally.