I've never had a good 'rare' burger.
Gross.
We have a local burger place -- best burgers in the business. But they do ask "How would you like your burger cooked?" Uhh, what?
How about -- done?
This is one of the reasons I grind my own burger meat. Based on
what Amazing Ribs says, rare burgers are dangerous burgers...
In meat, E-coli comes from fecal matter in the intestines of the cow. It gets on the surface of the meat during butchering from (1) fecal matter that is on the hide because feed lots are crowded with cattle and their waste, (2) fecal matter in the intestines if they are accidentally sliced open during butchering, (3) fecal matter that spilled from intestines onto the floor of the slaughterhouse or butcher shop, or (4) from knives, grinders, other equipment, other meat, or hands that have come in contact with fecal matter.
E-coli O157:H7 is primarily a problem in ground meats, not steaks. It is found only on the surface of the steaks. They do not work their way into the muscle or fat far beyond the surface. They die rapidly when you cook a steak’s surface past 160°F, even if the interior is red rare. Even if your grill is at a low 225°F, the exterior of a steak will hit 160°F fairly quickly and be safe. The problem arises when meat is ground. Then the outside gets inside and rare burgers or medium rare burgers carry risk with them because they are not cooked to 160°F. Because grinding is how the bug gets into the meat, E-coli is a problem for all ground meats and sausages unless they have been pre-cooked like hot dogs.
So... Once you grind beef, you've now distributed anything dangerous to the inside. Which means you have to cook it well enough to kill whatever it is, or take your chances.
So I generally cook burgers to about 150*. Now, you might say "well that's not safe either b/c it's not 160!" but it's not really true. "160" is the golden temp because at that temp, the bugs are dead instantly. But they die at lower temps too, it just takes longer. At 150*, it takes about 80 seconds for the temp to kill those pathogens. Since I rarely go from "on the grill" to "in my belly" in <80 seconds, 150 is plenty. (It's also the reason you can cook proteins at MUCH lower temps for longer time with sous vide and be perfectly safe. I could cook you medium rare chicken and it'd be perfectly safe, albeit probably disgusting.)
But surely, those burgers come out dry, right?
Nope, and hence why I grind my own meat. You try to make a burger with some lean ground beef from the store, or even 80/20 ground beef? Yeah, cook that to 150+ and it's probably going to dry out. You grind some chuck roast without taking out any of the fat, or a mix of chuck roast and brisket point? Oh, you're gonna have some beautiful fat in that sucker, and that burger at 150+ is going to be dripping juices.
Grinding my own, I can better control what meat is used and how fatty it's going to be. I can also control the coarseness of the grind, as I like a coarse grind which helps the patties keep from over-plumping when cooked. And I have a burger press, so I can weigh out the beef and make them uniform in the press so the burgers are all identical in size and shape, and thus cook evenly.