”Stunt casting” is the scourge of Broadway: Come to the Cabaret with Brooke Shields! Do the time warp with Sebastian Bach! But damn if the concept didn’t produce miraculous results in at least one instance this year. We all knew country superstar Reba McEntire, 46, would sing the gosh-darn-heck out of Irving Berlin’s great faux-hick musical, Annie Get Your Gun. And, given her Oklahoma skeet-shooting background, odds were good she’d pull off the accent and grapple with firearms even more convincingly than Ethel Merman, Bernadette Peters, and other Okies who preceded her in the part. But to make Manhattan’s most hardened critics chortle and cry? (The reviews in the New York Times, New York Post, and Daily News couldn’t have been more slavish if they’d been written by her fan club president; they helped breathe SRO life back into a revival on the verge of its last rites.) In a role that can make the wrong performer seem vaguely ridiculous, McEntire managed to be as spunky as any high schooler who ever essayed Annie — while lending the role some midlife poignancy. She was one part Loretta Lynn, three parts Lucy, all lovable. No one was ready to call this admitted theatrical dilettante the new Elaine Stritch just yet — and the role was just kin enough to Reba’s corn-fed persona that it could be written off as ”Doin’ What Comes Natur’lly” — but if she decides to take on Sally Bowles or, say, Rocky Horror’s Magenta next, we’re there.