So is BIG BORE RIFLES the book by Michael McIntosh? Or somebody else?

Am a little puzzled by your last paragraph. Do you mean you've killed a bunch of game larger than deer and pugs with a "286 JHP" or your "homebrewed" GGCB? Or that you've killed a bunch of deer and pigs with them?

Yours,
John

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck