Follow steps 1 through 4 of Canning Instructions, using six pint-size jars.
Coarsely chop peaches; you should have 5 1/2 cups. Coarsely chop or mash raspberries; you should have 2 cups.
In an 8- to 10-quart pan, combine peaches, raspberries, lemon juice, butter (if using), and pectin. Bring to a rolling boil over high heat, stirring often. Stir in sugar; when mixture resumes boiling, stir for exactly 4 minutes if using MCP pectin (1 minute if using Sure-Jell or Ball Fruit Jell).
Remove from heat immediately.
Skim and discard any foam from jam.
Follow steps 5 through 11 of Canning Instructions, leaving 1/4 inch of headspace in each jar and processing jars for 5 minutes (see notes).
