I didn't have any rodeos, but all shots were through the ribs. I try to take the bundle off the top of the heart. The holes in the lungs were tears and approximately 2" across. Up close I got a exit just less than a quarter, one didn't exit at a little longer distance, probably 140ish. I didn't find the bullet. They did die quickly but very little blood if tracking is going to be an issue.
I can use whatever here, and switched to 64gr BSB for that gun. It's a slow twist m77. The Hornady 55gr spire point works wee to. Velocity matters on the copper.