ANSWER:
The 8x57 blew through the tree every time, with both bullet weights.
Alas, the mighty .405Win did not go through.
So what I would say is I am not surprised that the .405 didn't go through, due to it's wider frontal area. Plus it is a flat point. Perhaps the spitzer would do better?
I was surprised that the 220gr Sierra blasted through the tree. I am surprised that the 200gr Accubond did. I thought due to it's higher velocity and lighter weight that it would not be able to penetrate.
One thing I noticed was how tiny the exit hole was for the 220gr Sierras. The exit hole from the 200gr Accubond looked as though the bullet had expanded some, yet still went through.
So the only concern I have after doing this is I'm wondering if that 220gr Sierra will expand sufficiently on a bear. I think I heard someone say that it was developed for the 8mm RemMag (velocities). Anybody know anything about that?
I am not concerned about the .411 cal., 300gr Hornady, or the .323 cal., 200gr Accubond bullets performing on black bear. The Accubond is one of my favorite bullets, in any caliber I have tried. It's accuracy is superbly consistent, and it expands reliably on game. Retains about 70% weight, which I think is ideal.
I suspect the 300gr Hornady will produce "bang-flops", pretty much the same as the old faithful .45-70.
FYI:
I am going to carry my M-1895 .405Win, plus my 2 8x57's, my M-98 Oberndorf Mauser and my M-700 Classic with me this spring, for black bear.
I sure hope I get a chance on a big bear.
Both the M-1895 and the M-98 have iron sights. In the ideal situation, I will grab the .405Win and try to stalk close enough for a shot. Going to see about making some shooting sticks to use.
I would use the scoped M-700 if a chance at a monster bear came up and I didn't think I had time to stalk close enough, in which case I would grab the 200gr Accubond for that.