frnkeore
Frequent Elocutionist
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Posts: 7658
Location: Central Point, OR 97502
Joined: Jun 16 th, 2010
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Re: Enlarging bullet mould cavity
Reply #40 - Jun 18th, 2019 at 5:34pm
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Fitz, I have my own story, similar to yours. The year after I got into this game (1986), I got a very good friend to start it, also. The rifle I started with was a Clerke HW, with, what I thought was a Douglas, 16 twist barrel. He found a local DST HW and I told him to to get a 16 twist 32 cal, Douglas barrel and he did. I also told him to call Ron Long and get the same 1.16 long, spitzer mold, that I had and he did that, too. Well, as you can imagine, his bullets tipped, a lot but, it shot 240/243 @ 200. At that point, I measured my twist and it was 15, not 16! So, I did some calculating and modified the Green Hill formula, to match my 15 twist, 1.16 long bullet. That changed the constant from 150, to 175. I applied that to the 1.16 bullet and 1.110 was the answer so, I also shorten that mold .050. And it stopped tipping and was competitive with my rifle. I bought that rifle/mold combo, when he stopped shooting, do to health issues and the pictured results it what it did for me in a match. The .862 group was in the CF match not RF. You'll note that I said that stability is a product of length AND center of gravity and that is why a 1.11 long, 4 caliber spitzer will stabilize in a 16 twist. Frank
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