My first mistake was to heavy of a all copper bullet. 200gr Barnes LRX went through a cow elk and also hit a rib don't think every opened up by the look of rib. Only good thing she ran all the way down the mountain piled up next to field where truck was parked. After that I dropped to a Barnes 175gr LRX 3 elk and 2 mule deer never ran more than 50ft. 2 dropped in there tracks. I am totally sold . 3 times now I have seen Nosler partions fail out in Colorado. Same with the nosler ballistic tip. But then again I am sure people had good luck with nosler I didn't.