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October 29, 2011, 10:41 PM | #26 | |
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Join Date: October 4, 2007
Location: All the way to NEBRASKA
Posts: 8,722
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Horsefeathers.
Quote:
"Boat Tailed" refers to the back end of the bullet. While a pointed bullet does make for a higher BC, so does a ..... ahem, boat tail ..... two different design features, both decreasing the drag coefficient of the bullet..... It is true that most (if not all) boat tailed rifle bullets have pointy noses (though many are pointy hollow point: "Open Tip Match" ring a bell?)..... but to say a hollow pointed bullet can't have a base that is narrower than the bullet shank is ignoring the fact that the XTP IS a hollow pointed boat tail. The bullet base is a smaller diameter than the shank..... this increases the BC of the bullet, and (I think more importantly) reduces the amount of bullet in contact with the barrel, reducing the coefficients of starting and sliding friction (See, Dr. Lutful Mannan, I was paying attention in Physics Class!).... |
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October 29, 2011, 10:44 PM | #27 |
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Join Date: October 25, 2001
Location: Alabama
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I stock up on the Hornady 147 RN boattails every time there is a "blem" sale.
I understand that the boattail is not for long range ballistics or for some effect on expansion of the other end, but to keep from bulging the brass when a long bullet is seated in a short case. |
October 29, 2011, 10:53 PM | #28 | |
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Join Date: October 4, 2007
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Quote:
2. The .45 has much more frontal area than the 9mm to resist pentrating a target..... while a 9mm HP can hope to expand to .45" .... a .45 is already there. |
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October 30, 2011, 03:45 AM | #29 | |
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Join Date: November 25, 2010
Location: Cincinnati, Ohio
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Good point jimbob, I didn't take into account surface area. I was focused on velocity and mass, but I see why now.
And the reason I didn't think 200fps is that much difference is because my nephews paintball gun is 300fps and it's not exactly deadly, so I had it in my mind that 300fps isn't very fast. I forgot how much a paintball gun can hurt though. I'm not arguing that a roundnose should have a higher coefficient than a hollowpoint, but in Hornady's manual, the 9mm with the higher coefficient is a 125gr HAP round, at .158 whereas the FMJ roundnose has a coefficient listed at .141 for a 124gr bullet. Any thoughts? I'm assuming it's from what I mentioned early. Quote:
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