Here is my recipe and it works out very well. If you want a smaller recipe just divide everything by the size batch you want to make except the yeast. I recommend the yeast listed as it will help eat more of the malic acid that Blackberries are high in.
Pour 1 gallon of warm water in a 7.9 gallon primary bucket or bigger.
Add K-meta, Yeast Nutrient, Yeast Energizer, Grape Concentrate, and stir well. Put all fruit in fermenting bag and squeeze over primary to extract most of juices and then put bag in primary. Pour the 1 gallon of boiling water with all dissolved sugar over fruit. Fill the rest of the way with remainder of room temp water and check SG, it should have a SG of around 1.085 give or take a little, if more then add a little more water, if less then add a little more dissolved sugar in small amount of water as sugars from fruit can vary a little. Let sit for 12 hours with lid loose or with a cloth covering bucket with elastic band or string tied around so as that not to sag in must. After those 12 hours add your Pectic Enzyme and wait another 12 hours while also adjusting your must temp to around 75 degrees. After those twelve hours, pitch your yeast either by sprinkling yeast, dehydrating yeast per instructions on back of yeast Sachet, or by making a yeast starter a few hours prior to the 12 hour mark. At this point either leave primary lid off with the cloth again, place lid on loose or snap the lid shut with airlock. Punch down cap twice daily to get all fruit under the liquid level. When SG reaches 1.015, rack to 6 gallon carboy and let finish fermenting with bung and airlock attached. When wine is done fermenting, (check a few days in a row to make sure SG does not change and SG should be around .998 or less) you can stabilize by adding another ¼ tsp of k-meta and 3 tsps of Potassium Sorbate and degas your wine thoroughly. You can now sweeten your wine if you like by using simple syrup which consists of 2 cups of sugar and 1 cup of boiling water or by using a juice or frozen concentrate. I typically take 2 quarts of an alike juice and simmer on stove at medium heat with lid off until its 1/3 its original size and let it cool to room temp and then add slowly to taste. Be careful not to over sweeten. At this point you can use a fining agent or let it clear naturally. Once clear, rack into clean vessel and bulk age more adding another ¼ tsp of k-meta at 3 month intervals or add ¼ tsp k-meta and bottle age for at least 3 months and enjoy. Longer aging will give you a better wine so save a few bottles till at least 1 year mark so you can truly see what this wine can aspire to.