The main variables that cause differences in weight from case to case are as follows:
- Material removed when cutting in the extraction groove.
- External head thickness
- Head diameter
- Sectional density of the webbing (the base of the casing)
Notice what each of these have in common? They don’t relate to internal volume.
That’s right – the main contributors to weight variances don’t have anything to do with internal volume consistency.
The more accurate, and tedious, way to measure internal volume is by volumetric water testing. But even then, if the meniscus isn’t identical each time, you can still have a reading that is off by as much as a grain.
Here at Peterson Cartridge we are acutely aware of the relationship between consistent internal volume and consistent shot placement. And we are told by extreme long-range shooters that our consistency is among the best.
Some of our competitors weight sort their casings as they come off the line. This ensures that the casings you receive have the most consistent weight from case to case. If that was one of the relevant factors to putting multiple bullets in the same hole we would do it also. But it is not.
If you’d like to prove this to yourself, try a box of our casings. Load and shoot them. Chronograph your muzzle velocities. Measure how tight your pattern is at the target. We believe you’ll be very happy with your results. Why? Because of extremely consistent Internal Volumes.