Well, I have information for 4 calibers.

The 9.3x74R should be about the same as the .30-06. The internal head area is .1164 in^2. Simply multiply this by the peak chamber pressure to obtain the back thrust.

The .405 is the same as the .30-40 Krag at .1134 in^2.

The .450/.400 is the same as the .450 NE at .1676 in^2.

The .375 H&H is .1385 in^2.