Preheat oven to 350F and move rack to top position.
Cook shrimp in large pot of boiling water with 2 teaspoons of the salt until cooked through (3-5 minutes).
Drain and rinse with cold water until cooled.
Pat dry and chop into bite-sized pieces.
Mix celery, mayo, chives, dill, mustard, lemon juice, Old Bay and remaining salt until combined.
Add chopped shrimp and mix well.
Spread butter on buns and bake on top rack for 3-5 minutes until toasted.
Top buns with lettuce and fill with shrimp salad. Serve immediately.
Nutrition Info Per Serving: Calories 475 Total Fat 19 g Cholesterol 203 mg Sodium 1883 mg Potassium 491 mg Total Carbohydrate 44 g Dietary Fiber 3 g Sugars 6 g Protein 32 g