I use sirloin as well when I make burgers. I chop it myself using a food processor… 30 and only 30 pulses so it doesn’t build up myosin. Makes for very tasty and tender burgers.
I love ground sirloin burgers. I went to Hollywood Florida to visit my grandparents years ago. There was a place called La Tubs on the inter coastal waterway. They served a 1 pound ground sirloin burger with provolone cheese on it. I don’t like sliced provolone but that burger was awesome. It was the best burger I ever had at any restaurant. I still remember it 35 years later.