By Ross Kerber BOSTON (Reuters) – Activist investors have asked Amazon.com Inc to review its sales of firearms accessories, concerned that the online retailer offers products that could be used to convert semi-automatic rifles into weapons that fire too rapidly to be legal. The shareholder scrutiny of the worlds largest online retailer comes a day before the anniversary of the school massacre in Newtown, Connecticut, where a gunman killed 26 people. The activists include the managers of funds that promote themselves as socially responsible investors, and a deputy of New York State Comptroller Thomas DiNapoli, who manages the states retirement fund. They sent Amazon Chief Executive Jeff Bezos a letter on November 25 and showed it to Reuters on Thursday.