Place 1 cup of berries in 8-quart heavy pot. Crush berries with potato masher. Continue adding berries and crushing until you have 5 cups done. Stir in pectin and butter. Heat on high, stirring constantly, until mixture comes to a full rolling boil.
Add sugar all at once and return to boiling. Boil 1 minute, stirring constantly. Remove from heat and skim off any foam.
Meanwhile prepare canning jars. Ladle into hot, clean half-pint canning jars, leaving 1/4-inch space at the top. Wipe jar rims and adjust lids. Process in a boiling-water canner for 5 minutes. Remove jars and cool on wire racks.