I think that Lapogus was the first in this long thread to mention that after a proof load is fired the barrel is measured with very sensitive measuring devices. The engineer or technician is looking for plastic strain or permanent deformation. Everything is a spring (elasticity, per Youngs Modulas) to the point of permanent deformation.
The tire test would be a form of proof test only if the barrel was measured (at many points) for deformation.
Lengthening chambers and forcing cones, backboring, and reaming metal to remove pitting are all modifications that do affect the strength of a barrel. The question is if there is enough metal remaining adjacent to the modified area so that the barrel will be safe with a SAAMI maximum MEAN pressure load. Yes, if one would read the SAAMI reference book they too would see that the loads are mean or average working or maximum pressure loads.
There are formulas for figuring the hoop stress of a closed cylinder (barrel with projectile being forced through it) just as there is for underground storage tanks. For fluid steel determining remaining barrel strength is a matter of working the engineering formulas. Now, Damascus steel is typically more ductile or elastic and thus more of a spring as Sherman Bell demonstrated with a small sample set of one fulid steel and one Damascus steel sets of Parker shotgun barrels, but that is another subject...
Good discussion,
Mark
Last edited by MarkOue; 12/09/11 01:38 PM.
