How do anda get Silver Rathalos tail in Monster Hunter Portable 3rd?

I want to get the gun chariot gunlance. I have everything i need except for the Akantor Jewel and 3 Silver los tails.
I have already cut the los' tail around 5-6 times already and whenever i carve it, I get los ruby atau scale instead. I also don't seem to get it in the rewards after capture. Am I doing something wrong atau is luck never with me whenever I take on Silver los?
Plz I need your advice!