I will assume that W.W. in Argentina is the same basic alloy as it is here in the USA.
If it is, you take 10 pounds of it and add 1 table spoon of Hornady high antimony shot to it.
Cast your balls out of this.
You will find that with a charge of about 120 gr of 3F black, these balls will go deeper than your pure lead bullets, despite the fact they weigh only about 270 gr.
If you cans the R.E.A.Ls. out of the same alloy they will go very deep. Deeper then the balls, but you may have to use a small mallet to start them. The only problem with bullets in muzzleloaders is that sometimes they go through animals in crocked paths. They will go deep if they are hard, but many times they don't go straight.