By Jack Money Business Writer jmoney@oklahoman.comAn investor that owns about 8.1 percent of Gulfport Energy Corp. stock sent its directors a letter Thursday that requests the Oklahoma City-based oil and gas firm launch a $500 million share buyback program. Firefly Value Partners also is calling for Gulfport to sell noncore assets including its 22 percent ownership stake in Oklahoma City-based Mammoth Energy Services and to add board members that would represent concerned stockholders. Firefly stated Thursday morning it sent the letter because of frustrations it has with Gulfport's board and leadership team in failing to maximize shareholder value. Gulfport didn't respond Thursday morning to an emailed request for a comment. "To date, we have been patient with decisions made by the board and management, and we appreciate the time that Gulfport's chairman and new CEO recently spent with us to discuss our views on the company," Firefly wrote. "However, as we previously communicated to you, we have been discouraged by the board's lack of urgency in addressing the company's prolonged stock price underperformance and its unwillingness to commit to actions that we believe would maximize value for stockholders."Read more on NewsOK.com