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Old November 13, 2012, 09:47 PM   #17
FrankenMauser
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Join Date: August 25, 2008
Location: 1B ID
Posts: 6,843
It sounds like you got lucky with those mistakes.
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A lot of people like to use light charges for fire-forming and "ease" the case into the shape of the chamber over 2 or more firings. But, I just see that as a waste of case life. Load it where it's supposed to be, and get it done. The quicker you can start working up a load in the fire-formed cases, the better. And, you don't waste as many bullets or as much barrel life. Obviously, if you don't have any previously known-good loads, you may have to work up to it, anyway.


Quote:
I was thinking about all those posts we see where someone says "If you're loading over book max, please stay away from my range!" while I was working on this project. I guess those people don't like wildcats much, since there's no such thing as "book max" or even minimum!
Yea. A substantial portion of the rifle ammunition on my shelves consists of a combination of components with no published data. Quite a few loads were developed by powder charge interpolation - analyzing and compiling data sets for other powders and/or bullets for the cartridge, or similar cartridges, and calculating a good starting charge. (It would be a lot easier to give the component companies a call, but that takes the fun out of it. )

My own 6mm wildcat build has me working at the opposite end of the spectrum, from your AI build. As I've mentioned before, it's a ".243 Win" chamber, but under SAAMI minimum spec by 0.002-0.003" in every dimension, with headspace of "zero". It's a near-perfect fit for already under-size R-P factory brass. The only expansion of fired cases is up to 0.003" (usually 0.001" or less), just above the case web.

But... because the cases don't expand and "cushion" any pressure spikes, I have to keep a close eye on load development. Max loads (so far) have always been reached below published .243 data. And, once primers start to flatten, sticky bolt lift and primer cratering show up much faster than my rifles with generous factory chambers. It really contrasts the performance of my massive "fish-bellied" .270 chamber, that eats over-book-max loads all day long.

Sometimes your goals just require you to color outside the lines.
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