Bucking wind vrs BC

[Guy Miner]

Good stuff there DF.

This, I understand.

 

[bullet]

Yes, like JD and I said, we are fans of heavy bullets that can be driven fast with good BC because they don't drift much with a cross wind and they retain energy and hit like a freight train. :mrgreen: :mrgreen: OH!! the math behind proving what I said??????? Exprience and Desert fox has demonstrated by experience what a lot of us hunters who have and do take long shots in the field on game know about the heavier bullet. :shock: :shock: :mrgreen:

OH by the way, absolutely great shooting Desert Fox, very impressive man, very impressive indeed, yes sir, you can shoot. 8)

 

[SJB358]

Awesome shooting DF..

I am not an ultra long shooter compared to a ton of you all, I just like heavier bullets! They work well and trajectory is easy to account for and the little extra help in the wind doesn't hurt a bit.. Great examples though fella's. Made is simpler for me to understand what all the math was about!

 

[Oldtrader3]

Ballistic Coefficient takes weight for area and ogive shape into account. It is, to make things simpler, espressed as a constant but it really is not. Heavier bullets for any given Ogive has higher BC. You have to measure BC at lower velocities and longer range because it is not really a constant. Air density (temperature etc.) count as well because air is subject to the Universal Gas Laws (Charles Gas Laws) and attitude (density). Corolius effects and gravitational earth spin effects also move bullets at several inches 1000 yards. Rh twist moves right, Lh moves left over long range. You really need a computer to do the integration math. No commercial canned ballistic program which I am aware of does polar vector wind calculations through 360 degrees, plus vertical vector. I guess snipers must have something close.

I ran my .204 Ruger against Winchester Ballistic tables for windage and drift and they were way off, even at sea level despite using the same bullets (Nosler BT's) and the same velocities that they advertized. Somebody is lying about something because they were off many inches. Additionally, if you blow a bullet many inches off windage course, you are shooting the hypotenuse of a triangle, not the right angle leg and your drop will calculate differently and be more because of the longer hypotenuse leg in the angle of the dangle. Sorry to get technical but this is pretty complicated.

 

[Desert Fox]

The problem with majority of these ballistic program and manufacturers published bullet B.C were base on drag curve model like the G1 which doesn't differentiate one particular bullet over another. Writing Ballistic programs algorithm base on this model will only work at shorter range. At longer ranges however, the accuracy will fall into the wayside. There are however few programs in the market, like the Patagonia Coldbore 1.0, that is base on analytic close form solution that does not rely on drag curve model. Instead it uses drag coefficient modeled as a function of mach number which matches the behavior of a particular bullet. It's expensive but worth every penny. I'm about ready to purchase the whole package.

 

[onesonek]

Thanks DF,,,that just reminded me of how much I have forgotten over the years, and how off base I can be also at times due to going from a poor memory.
With that said, I will agree with this as well,,,"You have to consider the whole flight regime of the bullet when determining how will it behave when subjected to wind. There's no commercial ballistic program out there in the market that can predict with certainty, the effect of wind on bullet. It's all approximation, so you can't rely on them. Empirical measurement and keen observation is much more reliable."
But I find one thing is certain,,,
nothing is for certain this side of the grave.

"like the Patagonia Coldbore 1.0"
Without researching it myself further,,,how does one compare to RSI Shooting Lab

 

[usmc 89]

Heavy high bc bullets ? litz's books are well worth the money if your wanting a laymens explanation of what's going on with bullet flight, drop, deflection,spin drift and any other deviation you can think of. I have both volume one and two but save your money and get the second edition this covers everything in volume one plus the new stuff and comes with a ballistic program. there is also a huge list of long range bullets with there specs and actual bc values. anyway interesting thread thank you.

 

[SJB358]

Heavy high bc bullets ? litz's books are well worth the money if your wanting a laymens explanation of what's going on with bullet flight, drop, deflection,spin drift and any other deviation you can think of. I have both volume one and two but save your money and get the second edition this covers everything in volume one plus the new stuff and comes with a ballistic program. there is also a huge list of long range bullets with there specs and actual bc values. anyway interesting thread thank you.

Where did you get the book from Jeff?

 

[usmc 89]

I got it from midway you can get it from Amazon also Scott. and spare yourself midways. ransom for shipping.

 

[SJB358]

Rgr, I will check them out..

Alright, I ordered it.. Hopefully it isn't lost in the mail.. The USPS seems to drop a package every now and then.. Hope it is a good read, I burn threw books and magazines out here. Only way to pass time when your traveling..

 

[ROVERT]

I'm sorry DF, but I feel like you really beat around the bush there. You can't beat physics and the ONLY things that dictate wind deflection are lag time and initial velocity. It's a fact.

Please prove me wrong with some hard evidence.

I'm really not trying to start a fight here, but it frustrates me when misinformation is spread around on the internet... I know, I'm in for a frustrating life.

I realize that published ballistic coefficients are not perfectly accurate and neither are ballistic calculators, but I'd bet shooters introduce far more error into the equation in their ability to read the wind accurately.

The only way that mass comes into play into wind drift is its use in calculating a ballistic coefficient or drag coefficient so that flight time can be calculated.

 

[usmc 89]

Rovert you are correct on the shooter introducing error and another undetermined variable. even though a proofed range card is present condition assessment is the key to precision.

 

[Desert Fox]

I'm sorry DF, but I feel like you really beat around the bush there. You can't beat physics and the ONLY things that dictate wind deflection are lag time and initial velocity. It's a fact.

My problem with this statement is that you're just narrowing it down to just these 2 known fact. I did not say that they weren't true. All I'm saying is there's more to it than that.

Please prove me wrong with some hard evidence.

I thought I did.
From my own observation, shooting at 1000 yards competition on a windy day, I find it easy to shoot with my 338 than with my 308, 7WSM or 6.5-47 Lapua. Somehow that 300 grain bullet stay true to the target. Why is that?

No harm, no foul here.

 

[bullet]

I have a couple of friends who shoot long distance matches and they say on a windy day the larger bullets used in larger calibers walk all over their 6mm and 6.5mm cartridges because the bigger caliber bullets have less drift. I have stayed out of this because I have really enjoyed reading this, but the fact is the heavier bigger bullets at very long ranges will have less drift and the evidence from my friends at their matches makes a strong case indeed, especially their ribbons and trophies. Desert Fox is correct in the final analysis.

 

[usmc 89]

Good deal Scott I think you Will find it interesting. Piles of how and why on all fronts. you and Brian Will have to stop through on your way to Idaho to shoot Joel Willhave a new gun to shoot and I Will have the 300 Norma sorted and possibly a 338 snipe-tac. I will think of some target challenge to make it interesting...

 

[usmc 89]

I have a couple of friends who shoot long distance matches and they say on a windy day the larger bullets used in larger calibers walk all over their 6mm and 6.5mm cartridges because the bigger caliber bullets have less drift. I have stayed out of this because I have really enjoyed reading this, but the fact is the heavier bigger bullets at very long ranges will have less drift and the evidence from my friends at their matches makes a strong case indeed, especially their ribbons and trophies. Desert Fox is correct in the final analysis.

I shoot matches every month precision f class and tactical matches if your friends are using a higher bc bullet than .612 which is found in a 140vld or a 618 bc in a 140 Berger hybrid they Will drift less assuming there going as fast or faster but to say they walk all over them that's untrue if you ever decide to shoot a match where there is timed strings of 7-10 shots per string of fire at varying distances pay attention to what the top guys are using I would bet there would be one of them using a 260, 6.5-284,6.5x47, or a creedmore.

 

[bullet]

Ok, I will respect your comments and also ask one of my friends in particular to give back his trophies. Also, I will keep myself out of this conversation since I don't compete in long range matches today, and when I did 30 years ago it was open sight military rifles, and for years taken game at long ranges from time to time. Frankly, I don't have the energy to pursue the things stated on this tread. I have enjoyed the read though, and once again respect your comments and understand even if I don't agree with your final conclusion. I will leave this to the experts on this thread, but will keep reading to see where it all goes. Oh, have you ever hit inside a ten inch circle at 1,000yds with and open sighted rifle?

 

[ROVERT]

My problem with this statement is that you're just narrowing it down to just these 2 known fact. I did not say that they weren't true. All I'm saying is there's more to it than that.

From my own observation, shooting at 1000 yards competition on a windy day, I find it easy to shoot with my 338 than with my 308, 7WSM or 6.5-47 Lapua. Somehow that 300 grain bullet stay true to the target. Why is that?

No harm, no foul here.

But there isn't more to it than that, that is all there is.

The reason that your 338 is easier to shoot on windy days is that the B.C. of the 300 gr. bullet is so much higher. That bullet probably has a B.C. of over .800, correct?

Bullets in the other calibers you mention struggle to make it out of the high .6's. The amount of advantage you have in ballistic coefficient allows you to give up some initial velocity and still have a shorter lag time... which is what it all comes down to. Mass, momentum, etc don't come into play here, just the lag time.

 

[onesonek]

I'm sorry DF, but I feel like you really beat around the bush there. You can't beat physics and the ONLY things that dictate wind deflection are lag time and initial velocity. It's a fact.
No, I don't believe he did. Only those two thing's are dependant on other inputs to get to that point of just velocity and time. Most of which wouldn't be a concern for the avgerage person shooting under 4-500 yds. When you start shooting at 800-1000 and beyond, then all the variables need to plugged in right. Just because he DF didn't go into detail, has no bearing on the issue.


Please prove me wrong with some hard evidence.
Just for a single instance, look at the different drag models. If you go by most published BC's being a G1 drag, when the bullet you are using, is say a G5 or G7,,,,at long range it is a factor. But I will venture a bet, that 99% of the shooter/hunters that use a Program, are just looking to get a close idea,,,again at normal hunting ranges it won't make that much difference. More will have issues getting a good read in the conditions of ranges inbetween the muzzle and target, in order to shoot the difference under 600 yds.. And while the physics and math behind Programs are pretty well set, the programmer and how the program is written may have faults, that can only be delt with by confirmation shooting. If nothing else, most are set up on inputs that are constant,,,,wind is not constant, and neither is the BC while in ToF

I'm really not trying to start a fight here, but it frustrates me when misinformation is spread around on the internet... I know, I'm in for a frustrating life.

I dislike misinformation too, ,,,that's not saying I can't get things wrong from time to time, Mostly due not refreshing my knowledge base. But be that as it may, I don't see DF misrepresenting anything. With his limited response,,,it's all in the details he didn't go into. I wouldn't write a book on the forum either. :wink:

I realize that published ballistic coefficients are not perfectly accurate and neither are ballistic calculators, but I'd bet shooters introduce far more error into the equation in their ability to read the wind accurately.
As early stated, I agree, and I'm sure DF would too, but that reallly isn't the discussion as being presented so far. Most aren't willing to spend the 100's and 1000's of rounds downrange to figure it out. But then too again,,,,most are not looking to shoot beyond normal hunting ranges. Those that are, I would hope are educating themselves, specially if getting into the long range hunting. But even with that, it still takes shooting, as a Program is no substitute, but only a guide.

The only way that mass comes into play into wind drift is its use in calculating a ballistic coefficient or drag coefficient so that flight time can be calculated.

Well, something I forgot earlier,,,, in relationship to the bore and shape, mass is also one component of figuring gyroscopic stability factor.

Aging memory suck sometimes,,,well, most times :lol:

 

[Oldtrader3]

Rovert, you are ignoring all of the other factors that effect bullet drop and movement off axis. I don't want to start a fight but I spent a fair amount of time trying to define the variables and you are saying they don't matter.

How do you compensate for direction twist, or Coriolus, or gravitational spin (even curvature at long range), or hypotenus, in your windage calculations and all of the others using only two elements for calculation? If the wind is east or west (shooting north), your trajectory will be different in each case.

If you read ballistician data sets, they mention all this as part of the calculation! I feel that you are either snowing us or oversimplifying.