To grill burgers and keep them juicy, you should use 80/20 ground beef as well as handle the beef minimally to form loose patties and keep the hamburger patties very cold until you grill them.
Also don't press the burgers or over flip the burgers when grilling them and cook the burgers over medium high heat like 375 F to 400 F for a couple of minutes per side until they are just done and then let the burgers rest briefly before eating or serving them to allow the juices in the meat to redistribute.
When grilling burgers you should flip a burger on the grill when the juices begin to bubble up on the top surface of the burger and the burger releases easily from the grill grate, which is often after 3 to 4 minutes for a sear.
For best results you should only flip the burgers once and use a spatula to check for a browned crust and ensure that the burger is springy to the touch.
When grilling burgers on the grill, a good rule to also follow is the 5 6 7 rule for burgers which is a guideline for grilling burgers, which helps you achieve consistent doneness of the grilled burger, which is based on cooking time per side.
This is assuming you have a 1/2 inch to 3/4 inch thick hamburger patty, over medium heat.
The 5 6 7 rule for burgers suggests that you grill the burgers for 5 minutes per side for rare to medium rare, 6 minutes for medium and grill the burgers for 7 minutes for well done.
This helps to ensure that you get a nice juicy burger on the grill without needing a thermometer.
5 minutes of cooking per side when grilling the burgers, produces a burger that is rare to medium rare.
6 minutes of cooking per side produces a burger that is medium done.
And 7 minutes of cooking per side produces a burger on the grill that is well done.
So if you want your grilled burger to be rare to medium rare, you would grill the burgers for 5 minutes per side.
If you want your grilled burger to be medium done, you would grill your burger for 6 minutes per side.
And if you want your grilled burger to be done fully, then you would grill your burger for 7 minutes per side.
Also don't press down on the burgers when grilling them, to prevent drying the burgers out.
And the 5 6 7 rule for grilling burgers also works best on a grill that is preheated to 350 F to 400 F with 80/20 ground beef.
And some interpretations of the 5 6 7 rule, define it as 5 minutes on one side, 6 minutes on the other side and a 7 minute rest period for maximum juiciness.