I believe the biggest is the Eastern which is what we have here, and the record was killed in Whitley County, actually Wolf Knob. It was an Eastern. I will let someone else answer the other two.
shock gobble means just what it says, a turkey will gobble when a sound or noise shocks or spooks it, usually during the spring. Owl calls, hawk calls, coyote calls, peacock calls, craw calls all will cause a turkey to shock gobble.