The Firing Line Forums Balistic Coefficient of a .54 cal round ball
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 July 22, 2000, 02:28 PM #1 R&H Member   Join Date: February 21, 2000 Posts: 48 I was just wondering if anyone here knew about what the Balistic Coefficient of a .54 round ball was in the velocity range of 2000 to 500 ft/s.
 July 22, 2000, 05:46 PM #2 Glamdring Senior Member   Join Date: April 23, 2000 Location: MN Posts: 1,388 BC= .00notgood What does it matter? A roundball is a 150 to 175 yard projectile [unless we are talking cannons]. You would have to test your ball's drop at 75; 100; 125; 150; 175; & 200 yards to KNOW what it is. Because what exact alloy and size [not to mention shape] mold you use would affect it. Checking actual bullet drop, in your gun, at known ranges is the only real way to know these things. If your wondering about ball vs connical the difference in velocity more or less balences out the difference in BC.
 July 23, 2000, 04:35 AM #3 JackFlash Junior member   Join Date: July 8, 2000 Posts: 107 OK, makes me wonder if I understand what a ballistic coefficient is. I thought it was the relation of the bullet diameter to its overall length. Educate me! (Thanks)
 July 23, 2000, 10:06 AM #4 Glamdring Senior Member   Join Date: April 23, 2000 Location: MN Posts: 1,388 The ballistic coefficient refers to how well a bullet maintains velocity [how streamline it is which is affected by shape and to some extent sectional density]. Or in other words how Aerodynamic the bullet is. Sectional Density is about how dense a bullet is in the cross section and other factors being equal [like bullet construction and impact velocity] bullets of equal SD will penetrate the same amount. Sectional Density [SD]= (bullet mass in grains/7000) / [bore diameter in inches squared] SD example for a 180 grain .308" bullet 180/7000=0.0257 .308 * .308=.0948 SD= (180/7000)/(.308 * .308) SD= .0257/.0948 SD for 180 grain .308" bullet=0.271 Hope that was clear? Now the Ballistic Coefficient of a 180 grain .308" bullet can be different things depending on shape and what velocity range you measure it over [drag varies with speed in air anyway IIRC] usually BC are estimated with an equation. But for some Speer 180 grain .308" bullets they [Speer] list BC's of "0.304", "0.540", "0.483", "0.352", "0.416" in their Number 12 reloading manual. Did that help any? hard to explain it over the net. If you have questions email me and I will give you links to Sierra or such I think they explain it there. Or pick up a reloading manual they cover most of this stuff in great depth.
 July 24, 2000, 02:17 AM #5 JackFlash Junior member   Join Date: July 8, 2000 Posts: 107 Thanks, I was getting BC confused with SD. I used to pay attention to SD in lead handgun bullets -- so the shorter/lighter ones have a lower sectional density than the longer/heavier ones. Now I'm finding out that some 7.62 X 39 ammo uses a bullet with a "plastic" tail section to affect ballistic coefficient. --Which would also affect sectional density. OK, I understand now!
 July 24, 2000, 06:02 PM #6 po boy Senior Member   Join Date: January 30, 2000 Posts: 145
quote:
R&H I,ve got a Hawkin 54 cal.coefficient simular to F 4 Phanom jet, a flying brick however with enough velocity does damm good job I shoot 100 - 120 grn loads and love itOriginally posted by R&H: I was just wondering if anyone here knew about what the Balistic Coefficient of a .54 round ball was in the velocity range of 2000 to 500 ft/s.[/quote]

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