Well let's see if I can remember everything off the top of my head without having looked at the new raws and such...
First you need to take the spiked ball and more or less copy and paste the thing and then rename the copy to something like... heavy ball.
Then you need to change its attacking type from piercing to bludgeoning.
Then you should have a complete item more or less.
Then you need to choose where you want to add your new reaction, like which building. I normally make a cheat building (as in my wiki or the thread.)
(I'm going to skip adding a new building, so we'll assume you put it into the smelter or some shiz.)
So you open up the build and copy and past an entry and work out that entry to be proper. This is a reaction, so when you load it up in the game, you'll be able to make it.
Then you need to add the reaction AND the item to the entity file.
I think that should wrap it up.
In the product line you can either cheat to make it out of thin air or actually use a reagent. If you use a reagent, you can add (Get material from reagent) don't recall proper wording... to the product line.
I can actually look through the RAWs again and make it for you, but if you plan on doing more modding, I'd rather that you learn.