Safety issue to the rifle or to the shooter?

My Krieghoff .458 once doubled unintentionally with no damage whatsoever to the rifle and only slight embarrassment to the shooter.

As I mentioned in a previous thread, the recoil of a doubling rifle is not twice that of a single shot, but four times, since the velocity of the bullets remains the same and the weight of the bullets combined is double that of a single bullet.

This means that since the weight of the rifle remains the same, the recoil velocity doubles, and the recoil energy varies with the square of the recoil velocity, hence instead of twice the recoil energy, it was two squared (or four) times as much, and instead of 60 ft/lbs of recoil energy, I absorbed 240 ft/lbs, but with no broken collarbone, sore shoulder or other complications, other than wounded pride at landing on my stern.

The bullets hit the target about 1" apart.

If I had been aiming at an elephant, I suspect his headache would have required four Tylenol instead of two to abate.