I was feeling flush, and wanted to make a burger so i had my butcher mince/grind up some sirlion.
I've tried sirloin in the mix and found it added a lot of expense but not much flavor. I was trying to figure out why some of the better restaurants include sirloin in the mix; Mitch (Weinoo) guessed that these restaurants all do their own butchery and use their trim for the ground beef. That's as good a guess as any of mine. If you don't happen to have a bunch of sirloin trim around, I wouldn't buy it specifically for burgers.
I'd say there are three factors in a burger blend: fat, flavor, and price.
-Burgers need 15% to 20% fat, depending on cooking method, level of doneness, and personal preference. You need to work it out so any leaner ingredients get balanced out by the fattier ones.
-Flavor is of course the whole point. Some cuts have much, much more than other. Some have flavor that we traditionally associate with burgers, others less so.
-Price: don't grind up expensive meat! As soon as you catch yourself walking toward the grinder with a dry-aged, prime ribeye, it's time to find someone to talk you down.
There's a reason we love chuck so much ... all by itself it fits all these criteria. It tastes good. Good quality chuck tastes like a good quality burger. It has the right amount of fat. It's cheap.
Something like tenderloin fails all three. It's too lean, has too little flavor, and costs too much.
When we add meat to the chuck, it's generally because we want MORE flavor. This should narrow things down quite a bit. What cuts have more flavor than chuck? Which ones would taste good in a burger? Which ones are fatty enough to hold up their end of the bargain? Which are cheap enough?
As I said before, my personal holy grail is hanger steak, but I think these questions could lead you in a few other interesting directions. Especially if your butcher ever has anything special on sale, or if you find yourself with a bunch of trim.