A few years ago there was a popular bolt gun wildcat that was a heavy hitter.
It was the .458X2inch American. Basically a bolt action .45-70 using a .458 WinMag case cut off at two inches.
That caliber with a 20 inch barrel would be a very good heavy hitter, and I think RCBS still makes reloading dies for it.
For those who have fought for it, freedom has a taste the protected will never know!
Or at least they did before political correctness