Preheat oven to 450°F (400°F convection oven). Pour 1 quart buttermilk and 3.25 lbs. of biscuit mix into a 10 qt. mixing bowl. Mix with a paddle at low speed for 25-30 seconds. (For hand mixing, use a bowl scraper or stiff spoon and mix until all dry mix is completely incorporated. Dough should be sticky to touch.). Turn dough out onto floured surface and knead lightly. Roll out to ½ inch thickness. Flour rolling pin and roll from the middle outward, using light pressure. For uniform thickness, ½ inch rolling pin guides may be used. Cut with a floured biscuit cutter. Do not twist cutter. Do not us a glass or blunt edged cutter. Place on a lightly greased baking pan with biscuit edges touching. Bake in pre-heated oven for 12-14 minutes, 9-10 minutes in a convection oven. Brush biscuits with melted butter after removing from oven.