(Reuters) - The coming weeks may well be a banner one for gun sales in America - and the massacre at a Connecticut elementary school will likely be a reason.The appetite for guns tends to increase following a mass shooting, according to a Reuters analysis of U.S. government data on background checks run on prospective gun buyers in the past 13 years - generally regarded as a reliable indicator of whether gun sales are increasing.Gun dealers say after such shootings some customers fear for their personal security, while others are concerned the events will spur new restrictions on gun ownership.