A group of Casey’s General Stores Inc. investors are urging the sale of the Ankeny-based convenience store chain, The Des Moines Register reported. In a letter sent to Casey’s on Wednesday, JCP Investment Management LLC (which owns about $45 million of Casey’s common stock), BLR Partners and shareholder Joshua Schechter said the company’s shares are “significantly undervalued” and do not reflect Casey’s “earnings power and full real estate value.” JCP, BLR and Schechter together own about 1 percent of the company’s outstanding shares, according to Casey’s management. JCP contends that Casey’s has missed earnings targets for seven quarters “due in part to decelerating same-store sales and bloated operational expenses.” Casey’s Chief Executive Terry Handley said Casey’s five-year shareholder returns exceeded those of the S&P 500 index and the S&P index.