Carteach is in the process of load development for Liberty, the M1 Garand. This entails shooting... lots and lots of shooting... but that's only part of the happiness. It also requires lots of hours blissfully spent at the reloading bench.
Part of the process involves case preparation. On this topic, books have been written... but not by The Fat Man. Here, just one small topic is being addressed.
In choosing which cases to run the load development with, the entire 30-06 inventory in play. That means over 1000 cases of different date and manufacture. Amongst them, a fair number of military casings.
The thing is, there is a 'Given' in the reloading world. It's been engraved in stone for so many generations that it's accepted as a golden rule. That is: Military brass is thicker and heavier than commercial brass. That means the interior volume of the case is smaller, so therefor the charge weight must be lowered or excessive pressures will result.
But.... is this rule so golden?
Today Carteach took a bullet for the team, and weighed several hundred cases, both commercial and military. The results were unexpected. Weighing the cases is a traditional way of separating out cases into lots of like-volume. The theory being that all sized cases have outside dimensions pretty much the same, so any weight variations must point towards differing case thickness, and thus differing internal volume. (As one intelligent reader pointed out to The Fat Man... metal density comes into play as well. He proposed a simple test for internal volume, consisting of filling the cases with water before weighing them. This makes sense, as the weight on the water filling the case will vary depending on internal volume of the case. This sounds like a wonderful excuse for further testing, and another article here....)
The bulk of the cases were divided into three major types. Greek HXP, Lake City, and Commercial Remington and/or Federal.
Here's the unusual part.... on average, the commercial brass was heavier than all the military. Both Lake City and the commercial were heavier than the Greek HXP military. This indicates the HXP does not have a smaller internal volume, but in fact has a larger one. This changes the whole ball game when loading with the Greek HXP brass.
That chart below shows a clearer picture of what was found:
Now, I know this isn't exactly going to be wildly interesting for those not deep into the intricacies of hand loading.... but for those us who share that particular addiction, it's fascinating.
N. Korea launches short range rocket for second day - Provocations
8 minutes ago