Sounds like a classic cup n' core jacket seperation to me. I have a buddy that will only shoot seirra GK's, every year he kills an animal and every year we recover a jacket or a core, very seldom both. He loves them and won't change I am wiating for the day he either looses an animal or has to put in several follow up shots. Like most have said before in the 243 and 6mm rem I load 100 gr PT, never worry about those failing. you did state that heart lung vitals were mush, if a bullet fragment had not punched thru the paunch, you may have had different feelings on the 100 gr hrndy bullet? After only using them on one animal and 2 rounds pretty hard to say not to use them at all. Your best advice to your friend was to keep the broad side shots or slight quater away shots. Confidence in your rig and gear is a definite plus, heading out with the thought of a bullet failure is probably not good charma.