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.357 Magnum with a Twist " UPDATED"

2K views 18 replies 10 participants last post by  mrerick 
If the primers were the same, they would not bother to manufacture and market multiple different primer types.

They may be very similar in physical size, but the chemistry of small rifle and magnum small pistol primers is different. In fact, there is a small difference in the size of small rifle and small pistol primers, but that is not the major issue here.

While the external ballistics measured by a chronograph may seem similar, this doesn't reflect in any way on the internal ballistics of the loads you're producing. In short, you don't have any evidence of the safety of the experiments you're performing. Since you're dealing with high pressures, that is always a potential safety issue.

I teach the NRA Metallic Cartridge Reloading course, and have certified students for about a decade. I would never recommend substituting primers like this unless you have the measurement tools to accurately determine the internal ballistics of the load (it requires an instrumented barrel). The reason the component manufacturers publish reloading manuals is to publish the results of their own measured experiments which have been found to have safe internal ballistics.

Internal ballistics are moderately complex. They involved a number of interacting forces, pressures, friction and firearm components. There are often multiple pressure peaks generated as a cartridge ignites, the bullet leaves the case mouth and jumps the gap to the leade of the rifling and then slows engaging the rifling. After pressure builds and the bullet finally starts traveling down the barrel other peaks can occur based on the speed of the powder burning before the bullet exits the barrel. The primer spark intensity and it's physical dispersion within the cartridge case affects ignition and initial pressure generation. Rifle primers are designed to ignite longer powder columns than pistol primers.

Substituting components like this without instrumentation is essentially experimenting with very high pressures blind. It's not safe, and I don't recommend it.
 
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