There is, indeed, more to this subject than first meets the eye. Many, many variables, some of them enumerated below:
Rearward force is computed using the ID of the case at the base of the powder chamber plus a variable that's dependent upon the angle & rate of departure of the case wall from the chamber floor, a variable so small that it's not really a factor in this discussion
Rearward force is also dependent upon the deformation resistance of the brass case at the head, that is, a case with thin walls like a Hornet will offer less resistance to stretching than a case with thicker or harder walls at the base
The body taper of the case is sometimes a major factor in the actual force applied to the breech face; owners of S&W M53 22 Jet revolvers or standard 219 Zipper rifles can attest to the fact that certain maximum body tapers tend to grip the chamber walls far more effectively than their minimum-taper brethren, which seems counterintuitive but is nonetheless true
The duration of the force is also a factor in the theoretical yield point of the action; a slap of Bullseye is more likely to damage an older rifle than a shove of black powder under many circumstances
These are only a few of the factors worth consideration.
Regards, Joe
