What determines your brass life is how much it is worked. each time it is fired the case neck should work more than the rest of the case. Having brass that fits the chamber with little work from a sizing die and periodic annealing a case could last a very long time.
If the shoulder and body are continuously sized .002" below the length and diameter of the chamber then it will not last as long as a case with a good fit. Custom dies made for a particular chamber to minimize the sizing will make for longer case life than an off-the-shelf die with a larger than minimum chamber.
Long case life also requires pressures that don't over expand the chamber but even mild loads that are sized in small dies and used in large chambers will fail early. It all comes down to how much work is put into the case. Each time the metal in the case is moved it gets a bit harder. At some point that hard case is required to expand beyond its elastic tolerance and it cracks. If the primer pocket expands then your loads are of a high enough pressure that you could lengthen the life of the case by lowering the pressure. Primer pockets expanding to the point of not holding a primer in less than ten rounds is an indicator to me that the load is too hot. For others ten loads is fine because they need the extra pressure to be competitive in the sport they follow. Giving up the life of the case in long range shooting is the same as replacing an engine in a dragster after two runs. Just the cost of being competitive.
If the shoulder and body are continuously sized .002" below the length and diameter of the chamber then it will not last as long as a case with a good fit. Custom dies made for a particular chamber to minimize the sizing will make for longer case life than an off-the-shelf die with a larger than minimum chamber.
Long case life also requires pressures that don't over expand the chamber but even mild loads that are sized in small dies and used in large chambers will fail early. It all comes down to how much work is put into the case. Each time the metal in the case is moved it gets a bit harder. At some point that hard case is required to expand beyond its elastic tolerance and it cracks. If the primer pocket expands then your loads are of a high enough pressure that you could lengthen the life of the case by lowering the pressure. Primer pockets expanding to the point of not holding a primer in less than ten rounds is an indicator to me that the load is too hot. For others ten loads is fine because they need the extra pressure to be competitive in the sport they follow. Giving up the life of the case in long range shooting is the same as replacing an engine in a dragster after two runs. Just the cost of being competitive.
