Droewors comes out to hard

[mtu1250]

Hi All
Maybe this topic was handled before by someone, I will appreciate the help. I have started making my own droewors, I use lean beef cut in small cubes, add sheep fat about 10% and mix in the ready mix spices, vinegar and Worcestershire sauce. I let it stand for a few hours, then I grind the meat and stuff in the casings, not to full. then I hang to dry for about 3 days. when its dry and we eat it, then it is very hard, the flavor is good, its just not as soft(fluffy or spongy) as the butchers, Does anyone have ideas of what am I doing wrong please