In a large bowl, combine breadcrumbs and milk. Let sit 2 minutes until the breadcrumbs absorb the milk and soften. This keeps the meatballs tender, not tough.

Add ground beef, beaten egg, garlic powder, onion powder, salt, and pepper to the breadcrumb mixture. Use your hands to mix gently until just combined. Do not overwork or the meatballs will be dense.

Shape into 24 meatballs, about 1.5 inches across. Place on a baking sheet as you go. They do not need to be perfectly round.

Heat a large skillet over medium-high heat. Working in batches, brown meatballs on 2-3 sides for 2-3 minutes total. They will not be cooked through. Transfer to a plate. This step adds crucial flavor but can be skipped if you are in a rush.

In your slow cooker, whisk together barbecue sauce, grape jelly, Worcestershire sauce, and hot sauce if using. The jelly sounds odd but melts into a glossy, balanced glaze.

Nestle browned meatballs into the sauce, spooning some sauce over the top. Cover and cook on low for 4 hours or high for 2 hours, until meatballs are cooked through and tender. Stir gently once halfway through if possible.

Switch to warm setting and serve directly from the crockpot, or transfer to a serving dish. The sauce will thicken slightly as it sits.