You know John, now that you say that, I do believe he was using the 180 FS, not the 180 Partition. It was along time ago. I have that kill on DVD.
I had 180 FS's fail to open from my 300 on a cow elk... tiny holes in and out, zero expansion. But she tipped over because both shots, from 325 yards, were within 6" of each other and both punched the lungs. However, she gave ZERO indication of having been hit.
I dislike mono's because of that other instances of failure to open.
Even when mono metals open they don't have that 6-8" path of initial destruction something like a partition, AB, or BT does. As such they simply don't kill as dramaticly.
