SIG SAUER P320 pistol

New Hampshire-based SIG Sauer makes the P320 9mm handgun.

Newington-based gunmaker SIG Sauer is facing a new lawsuit brought by 20 people — including federal agents, police and civilians — who say they were injured when the company’s model P320 pistols fired without a trigger pull.

The lawsuit is the latest in a series of legal complaints filed against the company, each claiming the pistol has a design flaw that leads to unintentional discharges of the firearm, occasionally while holstered. Plaintiffs are calling for the gunmaker to make safety design changes.