I have a white buttercream formula that I like that is made in a 20 qt hobart.

I would like to convert it to chocolate but if I just add coco it makes it too dry. Is there a conversion of some sort...... maybe less powdered sugar per coco???

I use the wilton buttercream recipe and when you make it chocolate you add the cocoa and then more liquid until it is the consistency you want.
For a small batch of icing - 1lb of sugar and 3/4 cup cocoa. Then it says to add 3 to 4 more teaspoons of liquid.
Not sure if this helps you since your batch is much larger... good luck!

here's what i do:
i make buttercream in a 5 QT. bowl...my recipe is almost enough for two standard cakes (2 layer)
so i'm sure you have to adjust, but...

3T vegetable oil, mixed to a paste with a 1/4 c. high quality cocoa powder.....
THEN stir into the BC....it's a mild chocolate flavor, i'm sure you could add more....

hope that helped...
sally

HEY, i live in Belton, too! Belton Texas

you can also add some hershey syrup with the cocoa to balance the dry.