Ground Sirloin makes the best burger.
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Not enough fat content for me in a burger made from sirloin.
I grind up my own from chuck. I really do want at least 20% fat content.
..with cheese & salad of course.
I’ve been watching a lot of the back and forth and I have to chime in here (sorry for the interruption/intrusion).
Generally chuck makes great hamburger, but if you buy larger cuts like whole prime rib and other fattier cuts of beef; when you butcher them you can save the fat in a vacuum bag for use later.
(Hint: sirloin makes great burger when you think ahead to keep enough fat on hand to make it the ratio you want). I freeze it for reuse up to 2 years later this way, works great. Sometimes butchers will sell excess fat as well.
Of course you want to avoid bubble gum fat, but you get the jist.