Place Ground Beef In A Large Skillet Over Medium-High Heat. Cook, Stirring To Crumble, Until Evenly Browned. Drain Off Excess Grease. Stir In Cream Of Mushroom Soup (Undiluted), Milk And Liquid Smoke. Reduce Heat To Low, And Cook Just Until Hot. Stir In Sour Cream, And Season With Salt And Pepper. Remove From Heat. Serve On Hamburger Buns.