Beef chuck and pork butt(shoulder) come from the same part of the animals. They are generally the lean /fat content for sausage making, I prefer NOT to add anything other than spices. Just like with every thing else, the less fat you have the dryer the final product will be. try cooking a hamburger made from 93% lean ground beef next to a hamburger made from 80% ground chuck and taste test them both. Back to the subject, 20% fat and add water enough to mix in all spices and mix well, when your arm is tired from the mixing, your probably done.