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Bucking the wind better BC or weight ?

 
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  #15  
Old 10-17-2004, 07:11 AM
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Re: Bucking the wind better BC or weight ?

Rick ,
Quote : Given two bullets with the exact same shape, one made of lead and one of copper, would they not have the same BC?

B.C. is a function of bullet shape and also Sectional Density . S.D. takes weight and calibre into account so the answer to your question is no as the above 2 bullets would have significantly different weights . Given exact same dimensions the copper bullet would have a lower B.C. .
If memory serves me correctly then given the same weight , calibre and ogive shape the copper bullet should have a higher B.C. and would be longer due to it's lower molecular weight .Don't quote me on that last paragraph. [img]images/icons/wink.gif[/img]
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  #16  
Old 10-17-2004, 02:45 PM
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Re: Bucking the wind better BC or weight ?

As said, BC is dependent not only on the shape, but the weight for a given caliber. It may be confusing, but it's really meant to simplify things for you by doing a bunch of math for you. Take a whiffle ball the same size and shape as a baseball. Which holds onto its velocity better when you throw it?
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>If you made another two bullets, one out of lead and one out of copper, that had the same ogive and boat tail, and weighed the same, wouldn't the copper bullet be longer and have a heigher BC?<HR></BLOCKQUOTE>
No. It would pretty much be a toss-up. If anything, the copper bullet would have more skin drag giving it a lower BC but that's such a small part of the overall picture it would likely get lost in the noise of stablization differences between the two out of any given rifle.
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  #17  
Old 10-18-2004, 10:00 AM
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Re: Bucking the wind better BC or weight ?

*******************
Okay...what would you rather hit a deer with at 1000 yards?

A 7mm diameter 180gr bullet with -218 inches of drop, 1366 ftlbs of energy, and 75 inches of windage, and time of flight 1.25 sec.
or
A 30cal diameter 210gr bullet with -246 inches of drop, 1322 ftlbs of energy, and 88 inches of windage, and Time of flight 1.35 sec.
******************************

Could it be said that the 7mm bullet with less recoil, less windage, less drop, and a shorter time of flight...you would have an easier time getting an accurate shot?
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  #18  
Old 10-18-2004, 12:56 PM
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Re: Bucking the wind better BC or weight ?

Trader

I think you're placing too much emphasis on BC. As you know, BC means absolutely nothing in 50 yard pistol shooting, but it has immense importance in 1000 yard target shooting. For all applications in-between those extremes, BC has varying degrees of importance and has to be given an appropriate value when making judgements as to the best rifle/cartridge combination to be used. In the example you gave (1000 yard deer hunting) I think I would give more importance to bullet construction than I would to BC. Neither of the two bullets you mentioned in your opening post are legitimate hunting bullets, IMHO. I would look for a combination that gave me a reasonably high BC, long range accuracy, all the velocity I can get, and good terminal performance at long range. You are likely to find several cartridge/bullet combinations that meet those criteria. Which one you choose is up to you. Keep in mind that those 1000 yard deer shots will be few and far between. How you intend to use the rifle the other 99% of the time is something to think about.

[ 10-18-2004: Message edited by: Cheechako ]
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  #19  
Old 10-18-2004, 01:02 PM
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Re: Bucking the wind better BC or weight ?

Yes... But who wants to shoot a seven mill?


Just joking.

IMHO the answer is yes. As it is presented the 7mm is a "better" way to go but in the real world the answer comes back to which of the two rifles will put the bullet the closest to that same POI most consistently? Will your spotter round represent predictably your "shot for effect" round? If the answer is "both are accepably simmilar" than it dosent really matter.

In a nut shell, the answer to "Which would I rather use?" would be "Whichever gun is in my hands at the time."
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  #20  
Old 10-18-2004, 03:20 PM
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Re: Bucking the wind better BC or weight ?

trader, I would go with the 30cal and a 210 or heavier bullet. At long range, impact vel drops way off. What does the damage is bullet diameter and momentum. You still need to hit fast enough to get some expansion.

When bullets slow down, the biggest diameter heaviest bullet is going to have a larger effect on that animal.

The difference in paper ballistics is slim. You still have to dope over 6ft of drift. A few more inches isn't going to change much. However, the heavier 30cal will make a stronger impression on impact.

All you have to do is go out and shoot milk jugs or water soaked phone books. It will be really easy to see the difference.

I have shot 165gr bullets out of 300Wby at 750yds at a dirt backstop. You could see the puff of dust through the scope. Hard to see with the naked eye.

My buddy would shoot his 45/70 and 500gr bullets at a whopping 1150fps. We didn't need a scope to see where the bullets landed. It was very obvious.

Now go heavy AND fast. YUMMM...

RBrowning, if you made two bullets of identical shape from your different materials/weight, the heavier bullet would have a higher BC because inertia is part of wind drift.

A heavier object will be less effected by wind then a lighter one. That assumes that they are both launched with the same velocity.

To get two bullets of the same BC from different materials or calibres, would require different shapes.

Bullets of the same BC will travel through the air the same ie a 6.5 bullet with a BC of 0.65 will drift the same as a 30cal bullet with that BC. Despite a huge difference in weight. Assume same muzzle velocity.

Jerry
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