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Anybody making creedmoor brass out of 22-250 cases? I have a metric shit ton of those.
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Let me tell you of my adventure in wildcat forming of brass for my 6XC. I made two batches both starting from the same lot of virgin Remington 220-250 brass. These were done before 6XC was available from anyone.
The first batch was formed in one pass through the die, as instructed. I fire-formed this brass within a few months using it for rapid fire strings in matches. It was excellent and is still in use today.
The second batch was also formed in one pass. This batch sat on the shelf unused for a couple of years (not loaded and not fire-formed). When I finally got around to loading and shooting the second batch, about 75% of the cases ruptured either at the neck or in the shoulder or both.
I tried annealing the formed but empty cases from the second batch but the results were the same - 75% failure rate with the same failure modes. There is some reason to believe annealing at a higher temperature than I used may provide the needed softening (1,000 F versus 750 F). I have not yet bothered to try, as I have a bunch of good cases.
Recommendations -
Try it! Do you know the sequence of operations to get from 22-250 to 6 Creedmoor? Is that the proper parent case to make 6 Creedmoor?
Use Imperial Sizing Die Wax. IMO, it is the best out there.
Start slowly with a small test batch (~50 cases, maybe a little less). Be sure to load and fire-form ASAP.
I hope this helps in some way.