The decision, which also sets an April 3, 2018, trial date, paves the way for depositions and potential access to internal documents from Bushmaster Firearms and Remington.
It would be the first lawsuit of its kind to reach the discovery phase after the enactment of the 2005 Protection of Lawful Commerce in Arms Act, or PLCAA, according to experts
"This is precedent setting in the sense that, after PLCAA, this is the first case against a firearms manufacturer under a negligence theory that looks like it might make it to trial," said Georgia State University law professor Timothy Lytton, who studies gun industry litigation.
The companies contend they are shielded under the federal legislation, which absolves gun manufacturers from liability if a firearm is "misused" in a crime to kill people.
The gun makers have until Friday to file a motion to strike the case, according to court documents.
"This is unusual," Lytton said of the decision's timing. "Courts normally decide first whether or not they think the legal theories are valid before they allow the parties — the plaintiff in particular — to run around and dig up evidence that might support their case in a trial."
He added, "In this instance what the judge is saying is, 'Go ahead, collect your facts before it's decided whether there are grounds to dismiss.'"
Judge Barbara Bellis last week denied Bushmaster Firearms and Remington's motion to dismiss the case but said the filing of a motion to strike the case would be more appropriate.
A source close to the defense downplayed Tuesday's developments as procedural.
"The reality is, every case gets a scheduling order with a trial date. There's nothing unique about what happened today," said the source, adding that defendants have filed a motion seeking to stay discovery.
Targeting young men
The families of the Sandy Hook victims argue that while the guns may not in themselves be unsafe
, Bushmaster and Remington's marketing strategy deliberately targets young men, some of whom are inclined to violence.
The families are demanding access to the companies' marketing documents.
The families also allege that weapons originally designed for the military have become common in the civilian marketplace.
The case has the potential to make history if it goes to trial. The 2005 Protection of Lawful Commerce in Arms Act grants gun manufacturers immunity from any lawsuit related to injuries that result from criminal misuse of their product.
On December 14, 2012, Adam Lanza fatally shot his mother and then drove to the school, where he used a Bushmaster AR-15 to shoot to death 20 children and six adults. Lanza, 20, killed himself as police approached. In all, he unloaded 154 rounds from the semiautomatic rifle.
CNN reached out to Bushmaster and Remington for comment but has yet to hear back.
Remington is the parent company of Bushmaster.