The articles in TFS about the successful quest for record groups in the unlimited pistol class raised a question for me. The competitor picked out a few "custom" cases that he felt were good enough cartridge cases to compete with. What would his criteria be?
the perfect case
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As I remember from arguing with Bob Birmley about it both in person and in the pages of TFS Bob picked out and prepared the cases as a guru for Mike McCaughan. Bob described how he did this in a TFS article with a title something like "Aiming for Records", "Shooting for Records" etc. I have just spent half an hour looking for the article without success so I hope others can give us a clue.
The tight neck chamber and case recommended by Bob is a well known successful technique for both jacketed and cast bullet custom rifles. However, some of the other procedures advocated in this article such as using only one case, although used by many past top shooters has never been shown to be useful by a well designed experiment but are still believed to be helpful by some.
John
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Thanks John, I'd like to read the article. I raised the question since I now have to make my own cases for my 308x1.625. The problem is getting the neck-chamber-bullet fit just right. I will get there eventually. But each case seems to be just a little different. Some turn out lose, other tight, too tight. Also even if we just want an inexpensive plinker, when we switch from jacketed to cast we usually change bullet diameters by as much as .003. That has to affect something. I mean we struggle with a .0005" mis-fit in the leade!
Was that article recent, say within the last year?
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Part 2 of the article is in journal no. 251. I hope this helps.
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Found it by accident "On the Road to Records" N/D 17 #250.
John
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Shooting a Savage 110S in .308, many years ago, I encountered hang-fires with the R-P -308 Small Primer cases while searching for light loads. Shooting ten-shot groups, there was one hang-fire per group., sometimes two. This was using Remington 7 1/2 Primers and Reloder #7 powder. Switching to SR 4759 and Varget in the 1600 / 1650 fps range produced the same phenomenon. Once this occurred, increased powder charges were shot again to confirm the observation Listening more closely, hang-fires were occurring in the 1700 fps range; going above 1800 fps cured the hang-fire occurrence.
As a control, I switched to Federal Match (nickel) Large Rifle Primer cases and shot the series again. No perceptible hang-fires in the range from 1600 fps to 1800 fps. This was with all three powders and duplicate loading.
I then shot the R-P cases with full loads and did not experience any hang-fires.
My conclusion was to use bulkier powder for lighter loads and to use the Federal cases in competition. There are too many other factors in combination to pursue this any further. Medium burning rate powders which fill the case at least 50% and assure more consistent ignition.
Farm boy from Illinois, living in the magical Pacific Northwest
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