There is a case to be made for blends of various cuts (a combination of short rib, brisket and sirloin, for example), but for consistency, simplicity and safety’s sake, you can’t go past chuck. Chuck has a meat-to-fat ratio that hovers around 80-20%, providing the ideal balance of juiciness and structure to the cooked patty. Blends need to be either mechanically mixed or ground twice; either option contributes to a temperature rise and speeds up the oxidation of the ground meat, especially its fat. This causes undesirable flavour compounds that we think outweigh any benefits of using varied cuts.
Chuck is naturally (in well-raised Australian “non-super feedlot USA style” cattle) about 17-25% fat (we have seen a lot it over the years!). This is a good range, balancing juiciness with a good final structure. We emphasise the word “range”, because we grind one chuck at a time from suppliers that raise beef in non-factory farm like settings. Beware of burger restaurants promising a certain ratio (ie 80/20). Either it’s B/S (every cow is different), or they have robot cows (unlikely, but we’re assuming robot cows could be any ratio you programmed them to be), or (like the supermarkets do) they are using trimmings and/or many different cattle per patty. You lose whichever way you spin it. You win when one burger is slightly fattier or leaner than the last one you had. Ideally your burger patty should be from one cow. The care and attention that goes into doing one chuck at a time bodes well for your end experience.