Traditionally, we have had our ground beef produced separated by cut - Ground Chuck, Ground Round, Ground Sirloin. Due to the processor issues of the past year, we've learned that a processor has to get special approval from the USDA to do that. One of the processors we use hasn't done that paperwork, so, on occasion we have... Ground Beef! This is not considered a 'regular stock' item.
Ground Chuck is the grind of choice for making hamburgers, no matter how you plan to cook them. Lean/Fat ratio of Ground Chuck is 85/15; this is a standard set by the USDA. Fat ratios are adjusted by trimming, and must fall withiin a two percentage point variance of the standard.
Ground Round is a star of versatility; if you don't know what you're going to cook, Round is a good choice. It still makes a great burger, but at 90% lean (again, USDA set standard) we do recommend oiling your grill or pan immediately before placing the burgers on. Its lower fat content means very little fat to drain if frying loose burger.
Ground Sirloin is as lean as it gets; at 93%, we don't recommend trying to make burgers with it, but it makes the best meatloaf you'll ever have. Any shaped/blended meat dish is a prime candidate for this grind; the low fat content means it will benefit from the moisture added by milk/eggs/water, etc - and not leave a greasy mess behind.
Ground beef, by USDA standards, must be a minimum of 73% lean. Ours usually comes out a bit over that, but in this case the rules are written as a *minimum*. The Ground Beef produced from our beeves is the same meats that would have been separated and labeled Chuck, Round and Sirloin - but all mixed together and not trimmed as closely.