longevity of 9mm vs. 357 Sig
It is my understanding that the 9mm versions of many pistols eventually benefit from most if not all of the design improvements regarding the stress of 40/357 models.
The Glock 19,32, and 23 all have the same outside dimensions and use the same weight of recoil spring. The addition of a second locking block pin is the only real difference of the 40/357 autos over the 9. No major change was needed to the Beretta 92fs to create the .40 caliber version 96. The 357 sig has an SAAMI maximum limit of 40,000 psi. The 9mm+P has a limit of 38,500. It is not uncommon for 147 gr. 9mm to generate pressures as high as lighter +p+ loads. Also, one doesn't need to shoot full power 9mm loads all the time. Since it is somewhat correct to think of a 40/357 glock as a bored out 9mm, I think the greater wall thicknes of the 9's barrel/chamber needs to be factored in. Bullet setback appears to be a greater cause of concern in the 357 than the 40 or 9. The 40 tends to have a problematic pressure curve. Both the 357 and 40 are capable of higher kenetic energy and power factor(recoil formula) than 9mm+P+. Therefore, I doubt that a 40 or 357 will last longer than a 9 even if a lot of +P or +P+ loads are used.
However,I am not a gunsmith or armorer. I do not know for certain if what I have said is 100% correct. This is based upon part of my reading and limited handling of these guns.