Sloppy Joes

1 lb groun beef
1/2 onion, chopped
1 T. mustard
2 T. brown sugar
1 T. red vinegar
1 t. salt
3/4 cup ketchup
1 can campbells chicken gumbo soup

Brown hamburger and onion.  Drain grease and stir in remaining ingredients.  Simmer uncovered 15 minutes.