Make the sauce: Combine the chili sauce, brown sugar, mustard, Worcestershire sauce, and vinegar in a small bowl, stirring with a whisk. Set aside.
Melt the butter in a large skillet over medium-high heat. Add the onion, bell pepper, and garlic and cook until the vegetables are tender, about 5 minutes.
Add the ground beef to the skillet and cook until the beef crumbles and is no longer pink, about 7 to 8 minutes.
Stir in the sauce and simmer until the mixture is thickened. Spoon the meat mixture onto hamburger buns and top with pickles.