ballistic coefficient calculations for the "lay" person

Kowotie

Kowotie

New member
I was on the beartooth bullets site and was working on determining the external ballistics for my particular load. There was a lot of the terminology used in determining external ballistics that I am not familiar with. Unfortianatly they offer no "Ballistics for the ballisticly challenged" /ubbthreads/images/graemlins/confused.gif section on there site. My questions are,

1. Ballistic Coeffieient: Simply, what is it, and how is it calculated?

2. What is Drag Function in refference to your bullet?

3. What are "Azimuth" "Elevation" "LOS" and "Cant" angles?
 
All those terms are almost meaningless to the average coyote hunter. Interesting stuff, if figures,and theories pique your interest. In the hunting field, outside of the absolute ludicrous long range stuff, BC is BS to my mind. A called coyote, at modest range cares not a wit, what the BC of the bullet your shooting is, that technical stuff comes into play at ranges where most of us shouldn't be shooting stuff at anyway:)
 
First of all no hard feelings,

Second , just askin a few questions here. Funny thing that curiosity, makes a guy as questions. This information is not to make me a better coyote shooter. Just looking to further my knowledge base. I've spent much time in the field and know what my gun and I can and can not do. And I am very carefull not to exceed these limitations. When I have a question, should it go unasked just because the answer almost dosen't affect the "average coyote hunter"?

I won't lie, it's almost hard for me not to take your reply offensivly. Like I said just asking a question.

Joey
 
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Chilerojo is probably correct in that no coyote has died or walked away because of bullet BC, etc.

On the other hand, if you're intrested in some of the things involved in why we make caliber choices, etc.,the attached link might help you get started.

The lady who runs this sight provides some basics along with some of the math involved. Hope it helps. - BCB

http://www.aeroballisticsonline.com/
 
Kowotie,

Never feel bad about curiosity no matter what someone else may say. IMHO it wasn't curiosity that killed the cat, it was ignorance.

For some, hunting is mainly about killing your prey and since most hunting can be done at short range (300YD or less), reloading for accuracy, accurizing firearms, etc, is a waste of time, money, and energy. In fairness, for some folks, especially coyote hunters, the challenge is to see just how close you can call them in but the resulting attitude is much the same.

On the other hand some of us enjoy challenging our shooting skills as well as our hunting or calling skills and that opens up the whole world of ballistics (and our wallets, LOL). I will pass up most prairie dog shots under 200-300YDs given the option of longer shots (my longest lasered was 703YD with a 22-250) and I bought a WT caller primarily for it's very long range remote function so I could set up to take long range shots on coyotes (I've killed them at 1/2mi with a .308 Police Sniper). I wouldn't take those kinds of shots on game animals but on varmints I enjoy the challenge.

To answer your original questions, Ballistic Coefficiant (BC) is a mathmatical comparison of how well a bullet resists the wind where a .50 BMG (I think) is rated at 1, so a bullet with a BC of .5 (wich is very good) would do half as well.

Drag function is the part of the BC calculation that is defined by the bullets shape.

Azimuth is the angle off of straight ahead, for instance do you need to correct a certain amount (MOA) left or right.

Elevation may be feet above (or below) sea level or how much correction up (or down) is needed depending on where it's used.

LOS is Line Of Sight.

Cant is tghe angle off of verticle that th rifle is held and is needed assuming the scope is leveled to the reciever.

Hope that's what you were looking for.

Good shooting

Leon
 
Yes, thank you Leon that helps a ton. /ubbthreads/images/graemlins/grinning-smiley-003.gif Thank you for your time and effort in explaining this to me.

And I don't find myself feeling bad. After all IMO the only STUPID question is the one that goes unasked! /ubbthreads/images/graemlins/smiliesmack.gif

Thanks partner, Joey.
 
Don't mind ol' red pepper, he can't help but offend. It just comes naturally.

Taking an interest in the how's and why's of your particular hobby or pursuit is natural and is something everyone should have at least a working knowlege of.

When somebody tells you it's useless knowlege, it usually means thier too lazy to find it out for themselves so you shouldn't worry about it.

The reason "most of us" have no business shooting anything past 200 yards is that "most of us" didn't take the time to do the work involved and have no idea what thier bullet is going to do at extended ranges.

Do your homework, practice your a$$ off, and when that smart old alpha is standing there giving you lip service at what he considers a safe distance, knock him on his a$$ and tell us all about it.
 
Well put Tony! /ubbthreads/images/graemlins/grinning-smiley-003.gif Copy that, Over! /ubbthreads/images/graemlins/wink.gif

Joey
 
I can't tell you how many times a little education regarding BC and drag and all the rest have come into my practical hunting, wheather it's on PD's, Coyotes, or Big Game. My farthest Muley was taken at just under 700yrds and I knew with reasonable certainty where that bullet was going to strike that animal. Knowing how much a load will drift, how fast it will lose it's energy, how fast it will fall, should be and is the basis for our sport. Nobody should be in the field without at least some basic idea of these parameters. From the point of view of making a clean kill or just safety, everyone should take a few days reading the basics, and learning them. I've been reloading more than 40 yrs now and I learn something new each day about "balistics". New bullets, new powders, different temps, different alltitudes, all affect a bullets path. We should know with as much certainty as possible where that bullet is going.

And besides that it's just fun.
 
As to how to determine the ballistic coefficient, the easiest way is to refer to the manufacturer of the bullet.

But it can be determined by using the velocities of the round from two different distances, say 15 feet and 100 yards from the muzzle. Don't recall the formula off-hand but some ballistic calculators have it.
 
Wrong Tony ole boy:), Ive studied and glossed over countless articles and data concerning BC, mildly interesting stuff, but when applied to hunting it quickly becomes a non-issue in most instances.My favorite gun rag author, Ross Seyfried, who has few peers in gun knowledge and experience, wrote a great article concerning BC,and basically stated what I had always thought, that for average hunting situations and ranges, BC is the least of your worries when pulling the trigger.
P.S...... Anyone who is "reasonably sure" where their bullet will hit at 700 yards, under field hunting conditions, makes me reasonably sure they are full of [beeep]:)
 
Why Rojo? /ubbthreads/images/graemlins/confused.gif Why must you insist on pushing peoples buttons and throwing your sarcastic know it all comments in, when a simple click could have led you away from this thread? And calling someone full of $hit??? /ubbthreads/images/graemlins/mad.gif If you dont like the question, don't answer! You can take your "average" attitude and thoughts on what I should be concerned with and apply them to your "average hunting situations". Really Good Luck! /ubbthreads/images/graemlins/grinning-smiley-003.gif

When I want to excell at something I strive to be better than average. If you'r content with the opposite then so be it. Each to there own. But don't patranize others who have different ideas and expectations of themselfs.

Regards, Joey
 
Let me see if I can make a point that should be pretty clear to everyone, including you Chile. /ubbthreads/images/graemlins/wink.gif

Even at mid-range shooting, BC matters.

Case in point: .270wsm
(I picked this particular cartridge because it's the last load I worked up and I have all the figures close at hand.)

The Sierra 90gr hp has a BC of .195
The Hornady 110 Vmax has a BC of .370

At 3600fps in a 10mph full value wind, the 90gr Sierra will drift about 12 inches

At 3300fps in a 10mph full value wind, the 110gr Vmax will drift about 6 inches.

That's at 300 YARDS!!!

6 inches is alot when you consider the range and target size that we deal with while coyote hunting.

When selecting a load, don't think that terminal performance is the end all when picking a bullet. The bullet can't perform if it doesn't hit it's mark.

That's like saying you don't need an accurate rifle to hunt coyotes. You don't, as long as you're gonna pass on everything past 100 yards. Same thing with BC.
 
Chili, Reasonably sure is the best anyone can do at especially longer ranges. To use tonlocuses example, what if ther is a gully or wash downrange where you would expext that the 10mph wind increases to 20mph for 50ft and how far downrange is it? Without a basic understanding of ballistics (including how BC affects trajectory) you effectively limit yourself to only short range (as tonlocus said) or have a greater chance of misses or wounded animals.

Or perhaps you were saying that you didn't believe anyone COULD be reasonably sure of where the bullet would impact at 700YD. I guess the guy that set the new 1000yd record last month in Colorado (10 shot 3.75" bullseye group) just got lucky? Nooo, I would tend to believe he was "reasonably sure".
 
Shooting from a bench with a rifle that weighs a ton and flags scattered from muzzle to target is not my idea of field conditions.

In the real world of calling, I would trade time for bc anyday.

Randy
 
Hello

Quote:
Do your homework, practice your a$$ off, and when that smart old alpha is standing there giving you lip service at what he considers a safe distance, knock him on his a$$ and tell us all about it.




That is great. Can I use that in my sig line, of course credit will be given.

Chili, back off! Knowledge is power.

JA in SD
 


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