Soak the hog casings in water according to the manufacturer's instructions.
Cut the pork shoulder into 2-inch cubes, trimming away excess fat and the bone. Freeze for 30 minutes.
Pass through a sausage grinder. Freeze 30 minutes.
Grind again. Combine with seasoning, beer and water. Freeze 30 minutes.
Grease the sausage stuffer horn. Slide the casing onto the horn. Place the ground meat into the hopper. When it reaches the tip of the horn, tie the casing into a knot. Continue stuffing the casing. Tie the other end in a knot.
Twist the bratwurst into links. Start by twisting away from you. Move down six inches and twist away from you. Repeat the back and forth twist.
Use scissors to cut into links at the point where you created the twist. If you notice any air pockets, pierce them with a toothpick.
Heat the grill to 350F degrees. Grill turning occasionally, until the internal temperature reaches 165F degrees.