Stir together the chopped shrimp and mayonnaise in a large bowl. Add the red onion, celery, bell pepper, tarragon, parsley, chives, Old Bay seasoning, salt and pepper, and stir to combine. Stir in lemon juice; cover and chill until ready to serve.
Open buns, but do not separate halves. Brush the insides of the buns with melted butter, and cook, butter side down, in a hot skillet over medium high until golden brown, about 2 minutes.
Divide lettuce among buns, and top with shrimp mixture. Serve with lemon wedges.
