Your Bovine Bash's have helped prove that the premium bullets like the A Frames & the solid Copper style bullet lead the pack when it comes to the really, really big animals.
A cast bullet can only stand so much stress & then it will fail, we found that out back in the 70's shooting Handgun Silhouette, the hard way.
Most all of us were having trouble knocking down the 200 meter Rams with our 44 magnums & so we tried going faster & using harder bullets, all we did was make matters worse.
What you need with a big animal & a big cast bullet on really big game, if that's what you're using is to slow it down a bit & give it a chance to work. Run it too fast & it will fail, we found out that fast wasn't the answer, "dwell time" on the target was the answer.
Still, a cast bullet is no match for the premium bullets on the mega animals if you're hitting big bones, they just won't cut it. You've proven you're wasting your time.

Dick