The idea was to invest heavily in the development of personalized weapons that could be fired only by a single person: the gun's owner. This was considered a nearly science-fictional proposition in the late 1990s, years before the world was filled with smartphones and finger sensors. But consumer backlash against the project drove the gunmaker to the verge of ruin, and Smith & Wesson recently told shareholders that the corporate bleeding touched off by this long-ago episode has never fully stopped. "Sales still suffer from this misstep," the company said in a February filing with the U.S. Securities and Exchange Commission.