Primers

I have some old I’ll say maybe 50 years old or longer small magnum primers, can I use them in my 9mm Luger
 

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Mike

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In most cases people can't even tell the difference between standard and magnum primers in regards to velocity, pressure signs or recoil. Magnum primers are supposed to initiate a longer flame in order to reach all the powder in longer (hence Magnum) cases. They still can't ignite more powder compared to standard primers in a best case scenario.

I'd keep them for display and nostalgic purposes.
 
Magnum primer in general are used with specific cartridges or with powders that are not easily ignited due to powder density such as ball powders. Anytime you change a component such as a primer type not listed with the load data one should always work up the load from scratch. Not all magnum primer are alike some are hotter than others and can cause pressure increases and with the 9 mm being one of the most sensitive to pressure issues I would definitely start at the minimum load data an work up slowly.

There are instances where the use of a magnum primer in small cases can start the bullet to moving forward before the powder has a chance to fully ignite which can cause some erratic velocity, ES and SD reading on the chrono.
 
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Magnum primer in general are used with specific cartridges or with powders that are not easily ignited due to powder density such as ball powders. Anytime you change a component such as a primer type not listed with the load data one should always work up the load from scratch. Not all magnum primer are alike some are hotter than others and can cause pressure increases and with the 9 mm being one of the most sensitive to pressure issues I would definitely start at the minimum load data an work up slowly.

There are instances where the use of a magnum primer in small cases can start the bullet to moving forward before the powder has a chance to fully ignite which can cause some erratic velocity, ES and SD reading on the chrono.
Good info! I use CCI mag primers in my 9mm loads and 45acp. Well, I use standard and magnum. I haven’t really noticed a difference. I’d assume powder would be a factor as well. Oddly, I haven’t chrono’d Standard vs magnum. I’m running well over base but under max, titegroup.
 
I loaded up some 9mm rounds using WSF with standard wsp primers and another bunch using magnum (wspm) primers and those loaded with the magnum primers were a little bit faster. But not significantly faster. I didn't save the results so I can't provide the numbers but the velocities were well within book values (pressures within the envelope for standard ammo). My conclusion was to shoot them. If I was using a powder with a greater nitro content and/or at max charge, I would consider the slightly added pressure. And, on the other hand, if I was using a bulky powder that filled the case, maybe the higher brissance of the magnum primer would ignite the charge better,
 
Below is a screenshot taken form the Lyman #48 Reloading Handbook using an identical .308 Win. load for testing. It illustrates the difference changing a primer can make in a given load and although the velocity doesn't change much the pressure rises quiet a bit enough so that if you are at or near a Max. charge weight you can easily go over pressure.

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Velocity is not always a good indicator of over pressure as you can see in the above screenshot. Using the spent primer itself is also not a good indicator as primer can show pressure signs even with normal loads or in some firearms even though the loads might be perfectly safe. I would suspect that Highboys Quick Loads program could shed some light on how different primer types in a given load affect pressure. Simply changing bullet seating depth on a 9 mm can have an effect on pressure.
 
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