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Post by ozark on Feb 3, 2010 19:43:09 GMT -5
Let me confess up front that I do not fully understand the BC of bullets enough to use that knowledge in the field. Or at the bench for that matter. This brings to mind a question. Does the average hunter/shooter need to know the BC factor? By that I ask if there is a way to use it to your advantage. I think it deals with how fast it loses velocity at sea level, a specific temperature and a specific density of the air over a given distance. During a discussion a sharp external ballistic expert could sound impressive by quoting various facts but would it help the listener who is like Ozark and not able to compute all the variables and come up with even a slight sight change to compensate. I admit I don't know enough to discuss it rationally. Should I try to improve my knowledge here? If I did would it help me or someone who might listen to me?
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Post by whyohe on Feb 3, 2010 19:54:19 GMT -5
I like you ozark dont know a whole lot about BC of a bullet. IMO the average hunter its probably not a big deal. but to a hunter that starts shooting OVER 150- 200 yards it becomes a concern.
also it may become more of a concern for big bore shooters. IMO again as a general rule you get those larger bullets/calibers they move slower and drop faster , so the better you can get them to cut threw the air the less they drop and the more energy they can retain at distances.
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Post by deadeye on Feb 3, 2010 20:11:56 GMT -5
b.c. is really a numerical number given to reflect a bullets ability to fly(to resist air),most average hunters probably dont need this especially the distance of shots is short,however some one wishing to tackle longer chores this comes into play but is in a gray area of advertising & only can be proved in the field. it is an estimate.if trying to entertain some might find this interesting but the very small percentage will grip it & apply,like the coriolis effect.
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Post by lunchbox on Feb 3, 2010 20:12:05 GMT -5
I would like to know more about the BC of bullets also. Any info on this post will help me out.
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Post by ozark on Feb 3, 2010 20:18:00 GMT -5
Maybe this thread will help some. I do know that we have members who look carefully at the BC when selecting bullets and even buying rifles. I don't know enough to see a number representing the bullet BC and decide if that number is good or not good. But the knowledge is among members in spades.
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Post by whelenman on Feb 3, 2010 21:14:50 GMT -5
Here's a good explanation of ballistic coefficients and their history and derivations for anyone interested. www.exteriorballistics.com/ebexplained/articles/the_ballistic_coefficient.pdfI think the biggest thing to remember about ballistic coefficients is that high velocity rounds of low coefficient are eventually outperformed at a certain range by lower velocity round of high coefficient.
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Post by ozark on Feb 3, 2010 21:49:52 GMT -5
Whelenman, I read it all. Maybe I understand better how little I understand. I got this: As the velocity decreases during flight the BC changes. I had figured as it slowed down to had to change. For me, with my personal brain limitations, it is to my advantage to remain silent about the BC factor and be thought a fool than to try to explain it and remove all doubts.
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Post by wilmsmeyer on Feb 3, 2010 23:17:00 GMT -5
OK. Here it is in a nutshell:
A very high BC bullet and a very low BC bullet will all be subjected to gravity at the same rate. Neither one "drops" less then another.
A higher BC buller will retain its' speed over distance more so then a lower BC bullet.
Shot at the same initial velocity, perfectly level with a level surface, they will both hit the ground at the same exact moment.
However, the higher BC bullet will hit the ground further away from the muzzle then the lower one....making the trajectory curve "flatter" because it covered more distance in the same amount of time. It defied the OTHER variables that affect flight....but NOT gravity. Variables such as profiles that cause resistence to wind. Dropping at the same rate but slowing at different rates due to resistence.
I agree that this matters not so much with book speeds and average hunting ranges...under 200 yds ... and average, common bullets.
But remember that the wind will also affect each bullet about the same from muzzle to ground. So the slow bullet that drifted 6 inches and hit the ground at 150 yds drifted at a larger rate then the higher BC bullet that also drifted 6 inches at 180 yds. At 180 yds, the slower bullet may have drifted 8 inches +/-.
Did that make sense?
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Post by youp50 on Feb 4, 2010 7:35:41 GMT -5
I believe that BC is an imperfect number that may be fudged somewhat by a manufacturer. Similar to the way that muzzle velocity is. Not that the numbers are not true, its just that the hunter may not be able to duplicate the conditions the manufacturer used to get these numbers.
I believe that some rifles can cause a bullet to perform better than the BC and Ballistic calculators say it should. Not by defying physical laws, just getting a better spin and no yaw imparted at the muzzle.
I believe that BC tables are a great read. Similar to powder burn rate charts. I am certain that a ballistics curve generated by a computer, taking into account the changing BC with changing velocity, and muzzle velocity are a great aid in determining where the point of impact should be at a given range.
Few will disagree that the proof is in the pudding. Take it to the range and see what really happens at the distances you will encounter while hunting.
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Post by deadeye on Feb 4, 2010 9:17:05 GMT -5
ozark,you need to take this whole crew w/you in the siminar! i just did a bc check a week ago-subject 7mm 168gn berger vld hunting bullet,bc list .617 g1 drag function,velocity 3063fps.sighted in @ 204yds. run the charts went to the fields just to see if the berger was listed a little high which i suspected. my findings= 2 shots @ 500yds were deadon,then went to 840yds again deadon,was leaning into the wind a little as the chart implied again deadon,a rarity but confirmed bc was correct in this situation. wanted to go further out but not possible where i was.if you look at the sierra program they list bc's @ different speeds,very interesting! i list the above not to impress someone but to show how to prove the bc,if it had been off could have went in to the ballisic program & altered the bc to match the actual drops recorded in the field,then log it for future approx true bc for another set-up
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Post by cfvickers on Feb 4, 2010 9:51:18 GMT -5
Berger doesn't mess around on their listed data. You will also find that if you email them with a customer service question, you will hear back directly from Walt Berger. They are a stand-up company.
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Post by ozark on Feb 4, 2010 10:12:42 GMT -5
Let me see.....Shape of bullet, speed of bullet, weight of bullet, altitude above sea level, density of the air, angle of elevation, yaw of bullet, wind speed, wind direction, gravitational pull. I have probably left out some important considerations but it is much to much information for me to worry about. My misses are all somewhere other than dead on target. Now, I can blame it all on BC and prevent misses from deflating my ego. Aint my fault, BC got me again. That is my excuse on all future foul ups.
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Post by deadeye on Feb 4, 2010 13:57:56 GMT -5
Berger doesn't mess around on their listed data. You will also find that if you email them with a customer service question, you will hear back directly from Walt Berger. They are a stand-up company. totally agree & his staff is sharp too!
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Post by chuck41 on Feb 4, 2010 14:06:06 GMT -5
After seeing the questions posed here I researched it extensively and discovered some really interesting information on the origin of the "BC". BC was the name of a stone age cartoon character that originated the "BC" coefficient of bullets that we use today.
He worked for the government and was charged with precisely weighing large domestic animals such as cows or sheep to weigh them at the local market. He found a good rock with a reasonably sharp edge on the top and balanced a strong log across it to act as as a balance beam. On one end of the beam he put a basket and on the other end he attached a harness to hold the animal and adjusted it so the beam was balanced perfectly level.
He would then strap the animal to the harness and put rocks into the basket starting with large ones and then smaller and smaller ones until the rocks perfectly balanced the weight of the animal. He then would complete the precise weighing of the animal by guessing the weight of the rocks.
And that is how bullet makers precisely measure the "BC" of bullets today.
If you get confused jus remember, long slim pointy ones get high numbers, short fat blunt ones get low numbers. BC is important to long range shooters, but doesn't really matter to those of us that usually shoot only 50yds or so.
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Post by whelenman on Feb 4, 2010 14:28:20 GMT -5
Yep, that pretty much sums it up. Tell the wife to check your medications. You're either taking too much or too little. LOL!
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Post by pposey on Feb 4, 2010 19:10:43 GMT -5
Inside of 200 it dosn't really matter if your shooting a centerfire at critters bigger than a rabbit,,, but those sleek little bullets sure look good with the plastic pointy tips and rounded boat tails,,,,,,
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