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ballistic coefficient on bullets

 
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  #8  
Old 12-10-2006, 02:33 PM
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Re: ballistic coefficient on bullets

[ QUOTE ]
The BC is the BC for only one set of atmospheric/environmental conditions. Change any of the atmospheric/environmental conditions and the effective BC changes. At least that's my understanding.


[/ QUOTE ]

Now that I can agree with.


catshooter quoted:

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Himidity, air density and temperature do NOT affect BC.


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Then catshooter quoted
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Actually... Mike and Roy are both on to it.


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RII quoted:
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The BC is the BC for only one set of atmospheric/environmental conditions. Change any of the atmospheric/environmental conditions and the effective BC changes.

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Mike quoted:
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And local BC will have to be adjusted for conditions, unless you have the means to adjust the drag curve. Depends on your ballistic software.
BC would be a constant with a matching drag curve(not G1), but because software available does not reference a matched curve for your bullet, under the specific -local conditions, apparent BC goes all over the place.
And worst of all, bullets are not made to ANY standard. Every lot is different from any maker. So their BC is bogus to begin with.


[/ QUOTE ]

So really catshooter, you agree that there are other factors than just form. Am I right.

That means to me that you just dont like me. You know, you say one thing then say another....
Did I piss you off somewhere?
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Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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  #9  
Old 12-10-2006, 02:47 PM
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Join Date: May 2001
Posts: 920
Re: ballistic coefficient on bullets



[/ QUOTE ] So really catshooter, you agree that there are other factors than just form. Am I right.

That means to me that you just dont like me. You know, you say one thing then say another....
Did I piss you off somewhere?

[/ QUOTE ]

What???... is your problem???

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In alot of cases (all cases), differant bullets will have a differant BC for a given powder charge, load density, barrel length, twist rate, velocity, air density, and I am sure a few other things we havent discovered yet.

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This is NOT true.


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It is almost always a waste of time to use the factories published BC for anything past 400-500 yards anyway.

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This is NOT true.

The following group was shot at 405 yards.

The rifle was built, and the first 35 rounds were shot to get the velocity, and 100yd zero.

Rounds 36, 37, and 38 were fired at the target (405 yds) based on come-ups dialed from a ballistic program...

http://www.snipercountry.com/images/....46-target.jpg

[ QUOTE ]
So you might as well just try differant bullets and figure out what they are dropping in what air density. Then cross referancing this real world data with a good ballistic calculator, you can come up with a real BC for your rifle/load combo.

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Back engineering BCs does not work, unless you have a lot of time on your hands.

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Published BC's are only an average based on a controlled enviornment and specifec barrel length/twist combo's.

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This is NOT true.

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Trust me,

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HA!!!

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it is no waste of time to fire away and figure out the real BC in the real world with your equipment.

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What you are talking about is developing your own drop chart - you are NOT developing a BC... so NOT true!


I don't either like or dislike you... I don't give a rats ass...

You need to get a grip and not let your fragle ego take hold of you.

.
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  #10  
Old 12-10-2006, 03:08 PM
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Re: ballistic coefficient on bullets

On a calm note,

I didnt say it was always a waste of time to use the factory published BC for 1K shooting. I said it is almost always a waste. Your example is of 405 yards NOT 1K. I dont doubt that you have used a factory BC and come out with a perfect hit at 1K. No proof needed here. I believe it. I have done the same myself. However, please dont believe that you can always use the published BC for every bullet and hit perfectly in every circumstance. I dont dont care what you believe or dont. Its your targets. Just please dont quote me and say it is absolutly not true unless you KNOW for a fact it is total bull crap. I can back up every thing I stated.

I am done arguing with you here and in every other post, Go ahead, swing away at me.
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Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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  #11  
Old 12-10-2006, 04:39 PM
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Posts: 920
Re: ballistic coefficient on bullets

[ QUOTE ]
I am done arguing with you here and in every other post, Go ahead, swing away at me.

[/ QUOTE ]

What the hell are you talking about... I have NEVER had an argument with you on ANY other post.

Are you mixing me up with someone else, or is it that everyone argues with you, and we all look the same?

.
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  #12  
Old 12-10-2006, 06:24 PM
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Re: ballistic coefficient on bullets

Not continuing to argue, just clarifying. Your're right, we havent argued in any other posts. I just meant, future posts. I will not be partaking in any future arguments with you. And no, nobody else argues with me here. Some have shown me where I was wrong, or even showed me another way to look at something, but no one has ever quoted me and yelled back that it simply wasent true.
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Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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  #13  
Old 12-10-2006, 06:48 PM
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Re: ballistic coefficient on bullets

New shooter,

sorry about the hijacked thread. Back to your original question, posted are some links to some good reads about BC's that are from more than reputable sources. These will help you understand the BC better and what goes into it.

The statment at the bottom of this first article sums it up very well.
http://www.shootingsoftware.com/coefficients.htm

http://www.riflebarrels.com/articles...efficients.htm

This last one is from Sierra and is most likely the most informative for most shooters interested in this topic.

http://www.exteriorballistics.com/eb...ned/4th/44.cfm

With this you should be able to draw your own educated conclusions based on credible scources and not mine or anybody elses.
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Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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  #14  
Old 12-10-2006, 10:34 PM
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Re: ballistic coefficient on bullets

I don't want to flare up a fire here but the barrel does have an affect on bc. The twist rate is directly responsible in part for the stability of the bullet and how it flies through the air. Understabilized bullets with a rated bc of say .7 obviously do not fly as efficiently as a properly stabilized bullet with a bc of .7 resulting in a much lower bc. On the flip side, a bullet that is overstabilized also has an altered bc because of the agressive yaw of repose and the nose might not follow the arc of the trajectory although it will be quite a small difference. Much smaller reduction in bc than if the bullet is understabilized of course.

Badly worn barrels also change the bc of the bullet as they degrade the aerodynamics of the bullet jacket. Over the course of the barrels life, you can usually see a small degredation of bc over time.

Now, for purposes of actually trying to hit a target, the shooter must know how air density and air temp among other atmospherics change the path of his bullet. Or just get a ballistic program and carry it with you in the field and it will correct the the trajectory for you and give the proper information.

Clear as mud right?
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