Shane Tuttle
Staff
This is the cover title on Shooting Times magazine dated September, 2009. The column is "Going Ballistic" by Allan Jones. Title: Mysteries and Misconceptions of the All-Important Primer.
It was an interesting read on primers in general. I'd recommend picking up a copy if you're not a subscriber. Here's a quick overview of some interesting tidbits...
1. Allan Jones, the contributer, is a former employee of CCI.
2. Commonly discussed is the primer ignites the powder, but it isn't mentioned very often that the primer also provides an initial boost in pressure to help the powder reach a burn that's self sustaining.
3. Jones tested loads from some propellant manufacturers that claim their products do not need Magnum primers. He loaded at starting loads as well as maximum normal pressures. This is where it gets interesting. Using Standard primers, max loads did not display ignition issues. However, higher extreme variations in pressure and velocity in the starter loads were evident. In extreme cases, short delayed firings roughly in the 20-40 millisecond range was detected. When he switched to using a Magnum primer, it "smoothed out the performance across the useful range of charge weights and completely eliminated the delays". This was something I didn't know anything about.
4. "CCI primer cups are harder than others". The real story: Dick Speer and Dr. Victor Jasitis developed a noncorrosive primer mix. In the early stages, they had one major difference from any othe maker at the time. The dried pellet was brittle. James states this wasn't an issue unless the reloader attempted to seat the primers too deeply. What happens is the anvil was "forced almost to the cup, and the brittle pellet broke away from the anvil". This also resulted in very little mix under the tip of the now overseated anvil. This mix was discontinued years before James even employed at CCI (started in 1987). I guess this myth sure dies hard.
5. Normally, most manufacturers have a small disk between the priming mix and the anvil which is made of "foil paper". However, it isn't made of foil. The term stuck, but the material didn't. There was true metal foil for the purpose of sealing early percussion caps. The paper used today burns ash-free by chemically treating it. Convenience of manufacturing is the only reason it's there. James' quote tells it best instead of me trying to summarize. "Wet primer pellets are smaller than the inside diameter of the cup when inserted and must be compacted to achieve their porper diameter and height. Without the foil paper, the wet mix would stick to the compaction pins and jam up the assembly process. The absorbent paper soaks up some of the moisture and binding agent from the wet mix and stays with the pellet when the pin is lifted at the end of the operation. It's the same reason you put wax paper between hamburger patties-it prevents sticking.
There are plenty of other misconceptions in the article such as "pre-stressing primers" and others. But I say get the magazine. Allan James' article isn't the only good thing in there that's worth the price of the magazine.
It was an interesting read on primers in general. I'd recommend picking up a copy if you're not a subscriber. Here's a quick overview of some interesting tidbits...
1. Allan Jones, the contributer, is a former employee of CCI.
2. Commonly discussed is the primer ignites the powder, but it isn't mentioned very often that the primer also provides an initial boost in pressure to help the powder reach a burn that's self sustaining.
3. Jones tested loads from some propellant manufacturers that claim their products do not need Magnum primers. He loaded at starting loads as well as maximum normal pressures. This is where it gets interesting. Using Standard primers, max loads did not display ignition issues. However, higher extreme variations in pressure and velocity in the starter loads were evident. In extreme cases, short delayed firings roughly in the 20-40 millisecond range was detected. When he switched to using a Magnum primer, it "smoothed out the performance across the useful range of charge weights and completely eliminated the delays". This was something I didn't know anything about.
4. "CCI primer cups are harder than others". The real story: Dick Speer and Dr. Victor Jasitis developed a noncorrosive primer mix. In the early stages, they had one major difference from any othe maker at the time. The dried pellet was brittle. James states this wasn't an issue unless the reloader attempted to seat the primers too deeply. What happens is the anvil was "forced almost to the cup, and the brittle pellet broke away from the anvil". This also resulted in very little mix under the tip of the now overseated anvil. This mix was discontinued years before James even employed at CCI (started in 1987). I guess this myth sure dies hard.
5. Normally, most manufacturers have a small disk between the priming mix and the anvil which is made of "foil paper". However, it isn't made of foil. The term stuck, but the material didn't. There was true metal foil for the purpose of sealing early percussion caps. The paper used today burns ash-free by chemically treating it. Convenience of manufacturing is the only reason it's there. James' quote tells it best instead of me trying to summarize. "Wet primer pellets are smaller than the inside diameter of the cup when inserted and must be compacted to achieve their porper diameter and height. Without the foil paper, the wet mix would stick to the compaction pins and jam up the assembly process. The absorbent paper soaks up some of the moisture and binding agent from the wet mix and stays with the pellet when the pin is lifted at the end of the operation. It's the same reason you put wax paper between hamburger patties-it prevents sticking.
There are plenty of other misconceptions in the article such as "pre-stressing primers" and others. But I say get the magazine. Allan James' article isn't the only good thing in there that's worth the price of the magazine.