In a large bowl crush the blackberries with a potato masher or the bottom of a heavy glass. Remove some of the seeds and pulp if desired.
Strain pulp you have removed in a fine mesh strainer catching the juice to be used to top off the remaining blackberry pulp and juice if needed.
Measure the crushed blackberries and juice. Top off the crushed blackberries and juice until you have 4 cups of berry pulp and juice.
Add the berry pulp to the pot with the sugar and stir to moisten the sugar. Turn burner on medium low, stirring occasionally.
Add margarine to the pot.
Once the sugar is mostly dissolved turn the heat on medium high. Continue to stir until the mixture comes to a full boil and continues to bubble up when stirring.
Add the packet of pectin, stirring continually and allow to return to a full boil.
Set a timer for 1 minute. Keep stirring for the entire minute.
Remove from the burner after one minute.
Fill prepared jars and process in a hot water bath for 10 minutes.