The Lawful Commerce in Arms Act is very narrow in scope. It only gives protection where a lawfully sold and purchased firearm (and all of the due diligence that goes with it) is used to commit a crime. It simply gives protection against suits that desperately try to build vicarious relationships with the person who commits the crime. 

The Judge in the Sandy Hook suit is allowing for the Plaintiffs to conduct Discovery. If this goes to trail then the start date is scheduled for 2018