Tom, The TSX Flatnose 45/70 bullet INSTEAD of a Barnes MZ is a lot better price:

https://www.midsouthshooterssupply.com/item.asp?sku=0003545843

$17.56. I got great accuracy with them in my Savage with a Crushed Rib sabot. I plan on tweeking my loadthat I foundlast year. The $17.56 is for 20, so that is cheaper than most of the MLing bullets out there that come packaged. This is 100 yards, with 44g of 5744 powder, a 45/70 powder. I don't believe it is superior to a Gold Dot, but I like the little "slits" on the inside of the bullet to make it expand perfectly at very low velocity and make wound channel large on thin skin game. Thefact it also shoots thru and leaves a gapping hole on the off sideis something that I like. I feel boom flops are better with this large a hole thru the vitals. I think a Gold dot will do the same thing, but the expansion will not start until well into the animal, I think the barnes will startexpansion right away because fo the slits in the side. I have seen that in ballistic gel somewhere,I think on a Barnes DVD.
Dead is dead, and I don't think that Barnes is superior to a Gold Dot, they will both do the job, accuracy is king, so if you can get a .458 bullet to fly better than a .452 pistol bullet (which is the case in my Savage), then use the more accurate bullet. As you said, shot placement is #1.
Chap