Rifle primers

Primers: types, sizes and the cartridges they work in

Primers may quickly be identified as one of three different types: standard, magnum or benchrest. How we use each type is a matter of considerable debate. 

In terms of size, primers for rifles are designated either large or small. 

Rifle primers
Primers are packed individually for good reason. Only remove them when you’re ready to insert them in a cartridge case

All will ignite just about any powder charge but one type of primer will provide a better outcome than another in any individual cartridge.

The recommendation for all ball-type powders is that it’s better to use a magnum primer. 

I believe a magnum primer is normally best for all powder loads over 50 to 60 grains. 

I have a friend, a former professional kangaroo shooter, who always uses a magnum primer, irrespective of cartridge size. In his opinion, they provide a better load. He did wear out several rifle barrels!

In my short foray into bench rest shooting, I used the 6mm PPC cartridge and benchrest primers. 

Before then, I used benchrest primers extensively in such cartridges as the .22-250 Remington, the .220 Swift and the 243 Winchester, each with lighter long-range projectiles. I still do. 

With such cartridges, I formed the opinion, rightly or wrongly, that the benchrest primers provided a smoother pressure curve.

Similarly, I have found that in some cartridges which should use a magnum primer, a standard primer seems to improve the group size and reduce extreme spread in velocities. Perhaps it simply flattens the pressure curve. 

I am not sure what a primer is worth in terms of pressure but for most cartridges, the extra velocity is somewhere between 50 and 75fps, based on my experience. 

You should proceed with caution when changing primers with any load. If you are operating anywhere near the maximum pressure, changing to a magnum primer could push you into dangerous territory.

If you do change a primer with a known load initially, you should drop the load one full grain of powder. Changing primers can and will alter velocity, group size and extreme velocity spread.

Rifle priming
Ron prefers to use a hand priming tool rather than charge cases

I note a trend among long-range target shooters to weigh primers. Obviously, weight differences point to varying amounts of priming compound. I haven’t tried it, up until now! I think that, perhaps, this is one of those intangibles that are difficult to measure but, overall, might contribute to the cartridge’s accuracy. 

There appears to be both a difference in weight between different sorts of primers plus a difference in weight between different batches made by the same maker. Slight, perhaps, but do we really know the overall effect on both velocity and, more importantly, accuracy?

You probably should handle primers while wearing a pair of cheap rubber gloves, but I must confess I’ve never done so, and I do not recall any misfires as a result. However, it is still a possibility, particularly if you suffer from excessively sweaty hands. 

When priming, I keep a minimum number exposed at any one time, and open powder should never be on the bench under these circumstances, whether in cases or a container. 

Normally I store my primers in their original containers in the gun storage area with the rifles. It’s cool, dry and seems to keep a constant temperature. Primers should not be loaded to another container and kept in bulk — it’s a potential disaster.




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Ron James