Thanks for that - very interesting! I had been wondering whether these bullets needed higher velocity to set up the hydrostatic bubble, but it seems not. I assume that in your comment on the "The performance difference of the 400gr Hydro compared to the 400gr FMJ from the 450/400 Nitro Express 3” on broadsides was very noticeable" you were referring to the Hydros vs the RNSP?

As to the other comments above on their usefulness for elephant, I wonder whether they will raise the performance level of cartridges like the .404 or .450/.400 which have always been noted for good penetration but offer less in terms of "knock down" effect on head shots compared to say the .458 or .470. Or is the real advantage on body shots? I suppose what I am really wondering is whether the hydros in a .40 calibre can make up some of the difference in "knock down" effect compared to larger calibres with heavier conventional solid 500gn bullets and greater frontal area. I'm sure many folks would like to know the same!