The FBI is returning to the ammunition caliber it labeled ineffective and blamed for the deaths of two of its agents during a 1986 shootout in Miami – the 9mm jacketed hollow-point luger.

In addition to the new bullet, the FBI has decided to purchase a new pistol to fire it, something that could be in the hands of the bureau’s 13,000 agents by 2016. The decision could also have far-ranging implications for local law enforcement agencies because they often model their procurement decisions on those made by the FBI.

The bureau dumped the 9mm bullet after the Miami incident because it failed to penetrate far enough into the gunman’s torso.

The shooter, former Army Ranger Michael Platt, then went on to kill two agents and wound a third. Though Platt was shot multiple times, an autopsy revealed that he died from the wound suffered from that first shot – one that penetrated his chest cavity but stopped just short of his heart.

In response, the FBI fielded a new pistol round, one they hoped would have better penetration: the 10mm. In the following years, the 10mm was ditched in favor of the .40 S&W, a stubbier round that could fit into pistols designed for small calibers.

Currently, the .40 S&W is a law enforcement favorite, but after recent studies on new 9mm rounds by the FBI’s Ballistic Research Facility, the 9mm is slowly finding its way back into the hands of police officers across the country.

According to FBI Special Agent Ray Cook, the bureau began considering a return to the 9mm round in 2007 in part because of advances in ballistic technology.

Cook says that the lighter the bullet, the faster the gun can “drive” the round into the target. For the FBI, that translates into 12 to 18 inches of penetration into the human body. The 9mm’s weight, Cook added, also increases an agent’s accuracy in a gunfight.