Tires are a very poor test medium for expanding bullets. The Hollow Point is designed to expand from fluid pressure. Penetration was half that of FMJ's? That does not surprise me at all. Do not feel under-equipped with this ammo. There is nothing "wrong" with your selection. Are Hydra-shocks or Gold Dots better, sure. Shot placement is the key anyway. Practice, practice, practice.
In life, strive to take the high road....It offers a better field of fire.
"Robo is right" Fuzzball