The Canadian government seemed to have went with the original factory load when determining the energy.

if the 500 Jeffery was loaded to the 460 Weatherby pressures it would easily break 10k jewels. so they ended up going with the original load and not the theoretical max possible pressure.

lucky for me the 500 Jeffery original load was 535gr bullet at 2400fps. that's 9,200j so its under the 10k limit

the only reason for the limit is they wanted to ban the 50 bmg / 14.5 x 114 up into the 20mm x 102 vulcan rounds. the 460w and a few of the other big bores got caught up in to it

Rule303, that is kind of where I'm at in the thinking, even a charging grizzly would think about a second charge if it was hit with a 500j.