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August 8, 2009, 09:12 PM | #1 |
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Myth Conceptions: The Primer is Exposed
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.
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August 9, 2009, 07:24 PM | #2 |
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Primer Article
Big +1 on that Tuttle8.
My Opinion on Shooting Times has gome way up since Allen Jones started writing for them. He has written some of the most interesting and informative articles I have seen in any mag in a long time. I believe he has been with them for about 8 months or so and if you can get your hands on any of the back issues they are worth the read, especialy the first few months when he writes about his time with the Dallas PD Ballistics Lab way back when. He definitly hit a home run with the Primer Article! JMHO
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August 10, 2009, 01:00 PM | #3 |
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Shooting Times was good enough to put it on their web site.
http://www.shootingtimes.com/ammunit...909/index.html (Fixed the link)
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August 10, 2009, 03:51 PM | #4 |
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It's good to see that ST has a decent writer--they hit the bottom of the barrel IMHO when Ken Oehler quit. The primer article was interesting as far as it went. It did not go far enough to make me open my checkbook and resubscribe. I spent my money on renewing Precision Shooting, where you can find much more helpful articles concerning primers and their use among other subjects.
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August 10, 2009, 05:39 PM | #5 |
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Tuttle8,
Interesting about the cup hardness. The author blames this on firing failures, but my impression of it came from the fact that even up into the early 90's I found CCI primers very much more difficult to seat into .45 ACP cases in my Dillon Square Deal than were their Federal and Winchester counterparts. So it was physical stiffness and not firing reliability. I have continued to assume that's how it is? I quit buying CCI because of that until the #34 and #41 came out, which are intentionally "military hardness". I still have a few of the old CCI pistol primers somewhere, but have no idea what year they were made? What I still have on hand would have been purchased closer to 1990. It is also interesting about the ignition of partially filled cases. Back in the mid-90's when I was shooting the M1A in matches, I tried out Accurate 2520 for one season. I was using Federal 210M primers in it. I discovered that deburring flash holes improved the consistency so much that groups at 100 yards dropped from 1.25" to 0.75". That is probably allowing the standard primer flame to accomplish some of what the magnum primers do, though I never found it made any noticeable difference in group sizes with stick powders. I also never tried magnum primers in the load. Today I might try the CCI #34, but I expect those to be harder since they are advertised as being so. Benchrest shooters always look for the mildest primers they can find, but they are also mostly shooting up near maximum with cases well-stuffed with powder. The idea is that the less influence the primer has on pressure, the more the shooter controls it with the powder charge and bullet pull. Primer pellets are remarkably accurately made, but as a percentage of their total weight, I would expect a full case of powder to be more precise.
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August 10, 2009, 08:18 PM | #6 | |
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Quote:
The term "hardness" is often used, incorrectly, for insensitive. Primer sensitivity is another matter. I have had discussions with people who made the assumption that since primers way back when were round and shiny, and they are round and shiny today, therefore primers have not changed. But the author states that primer characteristics change so often, that data is obsolete before the comparison chart is finished. We don't know about it, because the primer makers don't publish. |
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August 10, 2009, 10:54 PM | #7 | |
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You think you just had the last of the old lot, Unclenick? Before the primer scare, I was buying primers that one of my gunshop owners claimed was an average of being 1.5 to 2 years old.
Quote:
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August 11, 2009, 12:43 AM | #8 | |
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Quote:
I still use them. |
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August 12, 2009, 10:42 AM | #9 |
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Interesting observation. The only measurements for the cup thickness that I've found are the ones in the table you scroll down to on this page:
http://www.jamescalhoon.com/primers_and_pressure.php It makes them all look to be about the same, so the burrs and flaring may be the issue. I'll have to look. I found that taking the radius out of the bottom corners of a primer pocket with a depth uniforming tool, then using either the Dillon swager or the Wilson primer pocket profile cutter would make them easier to seat. A lot of extra bother, though. By the way, the article's comment on bridge thickness was interesting. For those who don't have one, the Forster Co-ax press (but not the Forster Co-ax bench priming tool) has a special primer seating ram arrangement that forces the primer to seat 0.004" below flush with the face of the case head to ensure that critical bridge thickness condition. I am unaware of any other priming tool that does this? I consider it worth the bother, with service rifle match ammo, to use that tool.
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