BRISTOL, Conn. — Even gun makers want to be liked. So governors and other politicians from states eager to embrace the industry have descended on places where they are not so popular — like Connecticut, Maryland, New York and Colorado — offering tax breaks and outright cash grants to persuade them to relocate. “I sensed an opportunity,” said Alan Clemmons, a South Carolina state representative, who traveled to Connecticut in the spring as part of a successful effort to lure PTR, a maker of assault rifles here. “They are not feeling loved right now in Connecticut. We’re delighted to have...