- Jul 27, 2011
In the “for what it’s worth category”, I found this primer data in a shooting magazine back in the 1990s. I thought you might find it interesting. I don’t remember the author, but if someone does, please post it so he gets the credit. As best as I can remember, here is what accompanied the data.
As I recall, the author wanted to measure what effect different primers have on velocity, extreme spread and standard deviation. He chose the 300 Winchester Magnum as the test cartridge due to its large capacity and his experience in loading for what he found to be a traditionally low SD cartridge.
10 matching cases were selected from a large batch of known consistent brass, matched to weight, trimmed to length, neck reamed and primer flash holes made uniform. The same 10 cases were used for each primer being tested.
A batch of quality 180gr bullets were chosen, and each were measured and sorted to weight. 90 bullets were then chosen that weighed & measured the same.
A slow burning powder was chosen that provided nearly 100% loading density and that had proven to produce a low extreme spread and SD in his 300 Win Mag experience.
10 rounds were carefully assembled using each primer, and the velocity, extreme spread and SD were then recorded. Shooting was done to equalize differences between sets. Don’t remember the details, but I suppose he allowed the barrel to cool between shots, and may have used an indoor temperature-controlled range.
I remember him noting that only the CCI primers produced a genuine difference between their standard and magnum primers. Most of the tested primers produced very little difference between their standard and magnum versions, and the Winchester standard primers even produced a higher velocity than their Mag primers.
Not long after this article appeared I bought 1000 Federal 210 primers to use in all my loads requiring a large rifle primer – due to the low SD and the fact that there was so little velocity difference (primer contribution) between the 210 & 215, but the extreme spread and SD difference were significant.
The shelf life for this kind of data is perhaps relatively short, due to batch and manufacturing differences over time. But then, maybe this data is still valid...