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7mm PRC
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<blockquote data-quote="jpndave" data-source="post: 1700058" data-attributes="member: 5437"><p>WOW Poeniceltic, that's quite a post there! You might want to get your own math in order before you go calling out errors that don't exist. As to length change if necking down only from 300 PRC to 7mm, follow along...</p><p></p><p>The diameter will change from 0.308 down to 0.284. That's a difference of 0.024 (0.308-0.284=0.024). Half of that is on each side so 0.012 (0.024/2=0.012). The length change is the tangent of the angle of the shoulder times the change in length subtracted from the original shoulder (since our shoulder angle is 30 degrees using Pythagorean theorem - which is pretty well established math - times our change in diameter) so 0.012/TAN 30 = 0.020785 (rounded to 0.021 for consistency). So the new shoulder length would be the original 300 PRC neck length of 0.308 minus our change going down to 7mm as you pointed out 0.308-0.021=0.287 give or take with the brass forming or trimming. So that .285 is close.</p><p></p><p>And just for fun and to make some sense of all this in case the math is confusing. Here is a 300 PRC case with a 180 ELD-M set at the 3.9" which I assume you meant even though you typo'd 2.9" in your post above as you used the 3.9" back in post #71. (Quoted below) To get that bullet out to 3.9" would take some SERIOUS neck stretch. You can almost get the boat tail in the case - our extra 0.021" will help a tiny bit. It may not be the longest 7mm out there but it is a long 7mm bullet.</p><p></p><p>[ATTACH=full]146908[/ATTACH]</p><p></p><p></p><p></p><p>Can we let this length issue and the "7-KAM" go, at least on this thread, please? Might want to apologize to Jud96 for running him into the ground on "flawed math" that isn't flawed.</p></blockquote><p></p>
[QUOTE="jpndave, post: 1700058, member: 5437"] WOW Poeniceltic, that's quite a post there! You might want to get your own math in order before you go calling out errors that don't exist. As to length change if necking down only from 300 PRC to 7mm, follow along... The diameter will change from 0.308 down to 0.284. That's a difference of 0.024 (0.308-0.284=0.024). Half of that is on each side so 0.012 (0.024/2=0.012). The length change is the tangent of the angle of the shoulder times the change in length subtracted from the original shoulder (since our shoulder angle is 30 degrees using Pythagorean theorem - which is pretty well established math - times our change in diameter) so 0.012/TAN 30 = 0.020785 (rounded to 0.021 for consistency). So the new shoulder length would be the original 300 PRC neck length of 0.308 minus our change going down to 7mm as you pointed out 0.308-0.021=0.287 give or take with the brass forming or trimming. So that .285 is close. And just for fun and to make some sense of all this in case the math is confusing. Here is a 300 PRC case with a 180 ELD-M set at the 3.9" which I assume you meant even though you typo'd 2.9" in your post above as you used the 3.9" back in post #71. (Quoted below) To get that bullet out to 3.9" would take some SERIOUS neck stretch. You can almost get the boat tail in the case - our extra 0.021" will help a tiny bit. It may not be the longest 7mm out there but it is a long 7mm bullet. [ATTACH=full]146908[/ATTACH] Can we let this length issue and the "7-KAM" go, at least on this thread, please? Might want to apologize to Jud96 for running him into the ground on "flawed math" that isn't flawed. [/QUOTE]
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