For years I just made my Mother's Sloppy Joe recipe. Then one day I decided to try it with some BBQ sauce. My family loved it so well that's the only way they want it fixed. It is super quick and easy to prepare. It goes great with slaw and chips.
Brown ground round; drain off any excess fat. (Ground round is so lean there usually isn't any excess fat).
Stir in ketchup, BBQ sauce, mustard, and onions. Simmer covered on low heat for 10 minutes. Stir frequently to prevent sticking. If your mixture seems too thick, add a little extra BBQ sauce or a Tablespoon or two of water.
Using heaping Tablespoons put the meat on the buns. Optional: If you prefer, you can mayonnaise the buns first; or simply put the mayonnaise out for everyone to add according to their preference).