Bucking wind vrs BC

[tjen]

OK you have the constent to target 90 degree wind. That said the faster bullet will have less wind drift. But what about real world mulit-directional wind and heavy bullets.

Will a 150gr .277" BT be better than a faster 130gr FB for bucking wind? Is BC all that matters just for ballistics (not terminal ballistic). You never know what direction the wind will be when you have a shot. Head wind 10degrees 20degrees 180 degrees etc. Seems to me momentum has to come into play and sometimes slower heavier bullets have more of it.

 

[onesonek]

There is a yes and no answer to all aspects to way the this is purposed. Range being the greater part of the yes or no answer. One can really only put so much stake in the number's,,,the real test is in the shooter and firearm, not so much the round.

 

[wildgene]

...what you need to factor in here is the lighter bullet looses velocity faster than a heavier bullet, BC is a measurement of how "slippery" a bullet is thru air, so in the "real world" unless you are moving the lighter bullet @ an extremely fast velocity, out there where BC actually starts to make a measurable difference, say 400yds.+, the lighter bullet has shed a lot more velocity, while the heavier bullet has retained more velocity, energy, & less wind drift...

 

[onesonek]

That too, I forgot that slowing part. Thanks Gene.

 

[Teknys]

I liked that term "Slippery" !!
I look at the BC number as the bullet's ability to pass through atmosphere and it's ability to resist change in direction (Wind).
As for fast light bullets (Low BC) compared to slower heavier bullets with a High BC.
I usually don't worry about BC if the shooting is less then 350 yds for "normal bottleneck" hunting rounds. It is usually around the 300 - 400 yd line that the higher BC bullet is passing up the lighter bullet which started out faster but is slowing down faster too. When you plot out drop and wind charts you can see where the trade off would be with your given load and then you can make a decision on what is right for you.
Like I stated earlier in this post: If my shooting is let's say 350 and less I don't worry about BC. Depending on what I'm using the load for it might be light and fast bullets or heavy and long.
I put more consideration into repeatable accuracy and bullet construction then I do BC. ... Except for my one long range toy, Sendero 300RUM and 200AB or 210 VLD.

 

[Desert Fox]

Depend on how far your shooting. At 400 yards or less, BC doesn't matter much. Beyond that however, BC will play a significant part in how your bullet will fare against the effect of wind. You've mentioned momentum. A heavy bullet with high BC and moderate velocity will have less wind deflection when compared with a lighter bullet at higher velocity but with lower BC. This the reason why I like to shoot with my 338 Lapua Ackley in a long range competition. The 300 grain SMK at 2812 ft/sec is much easier to shoot in a windy day than my 308 shooting the 155 grain Scenar at 2950 ft/sec.

 

[Guy Miner]

Wind bucking is one of the key reasons long range shooters favor high BC bullets.

Trajectory is pretty easy to figure. Real world shifting winds... That's the gremlin that sends bullets out of the X ring, into the ten, or nine... Or in my case the eight ring often enough!

A high BC bullet drifts less in the wind, and thus is highly prized by long-range riflemen.

 

[Horsethief]

The heavier-for-caliber, spitzer bullet will do better vs a cross-wind or quartering wind than the lighter bullet of the same design across the spectrum of chamberings. You may think your bullet has to get there faster than X-ft per second to do the amount of mushrooming or penetration you think is needed. In a 300 mag, a 180gn bullet will do better in any wind condition than a 150gn bullet. Same with the 150gn bullet in your 270 Win compared to a 130gn variety. As for the boat tail vs a flat bottom, as long as the bullets ar (a) supersonic and (b) not at ranges over 500yds, I have found them to be virtually identical in accuracy. Perhaps my testing and variables differ from others who have done this, but I will not hesitate to use a handloaded, 180gn Hornady flat-bottomed spitzer bullet vs any deer coming out of my 300 Wby Magnum.

The military snipers use 175gn bullets in their 308 Win and 300 Win Mag rifles. There are concentrating on accuracy, not velocity, since the bullet is going to do the job if they do theirs.

 

[ROVERT]

Will a 150gr .277" BT be better than a faster 130gr FB for bucking wind? Is BC all that matters just for ballistics (not terminal ballistic). You never know what direction the wind will be when you have a shot. Head wind 10degrees 20degrees 180 degrees etc. Seems to me momentum has to come into play and sometimes slower heavier bullets have more of it.

Lag time is the only thing that affects amount of wind drift. That is the actual flight time to target minus what the flight time would be in a vacuum. Momentum has no effect on this value. BC does. The only reason a slower, heavier bullet can drift less is if it has a significantly higher B.C. The direction of the wind makes no difference in terms of which bullet will fair better.

 

[usmc 89]

Rovert got it. time of flight. dictates drift, the longer the bullet is subject to a condition the more it Will be affected. the higher the bc the more efficient the bullet is at retaining velocity. gravity works the same way when using the term drop, a bullet Will drop the same at any given weight the difference is in how far it Will travel before it impacts. obviously a bullet that can maintain velocity better Will travel further in the same amount of flight time than a bullet that is less efficient. that's the bottom line getting the bullet from point a to point b the quickest.

 

[tjen]

I should have titled the post Wind Bucking Vrs Velocity. I have for termal effects as well as ballistics usually pick .245 to .280 SD bullet and feel they do better in windy condistions.

The first truly light SD bullets I have shot are the .224" 52gr bullets and you realy can see the differance at two hundred yards that wind effects them.

I ofton see the post asking what bullet for a caribou hunt and most repond back with 150gr for a 30-06 and I repond with 180gr Bullet like a AB or GK. I feel most worry about extra .5-1.0" drop at 300 yards and not winddrift or accuacy.

I seldom pratice shooting at the bench in 1-20 mph gusty winds and feel most others do not. If they did they may trend to heavier per caliber bullets decided due to consistent accuracy thuo 200-300 yards may not revel it well.

I still think its hard to beat the terminal performance of most RN bullets inside of 200 yards so you see were I come from. Is the BC at 200/300/400 yards even listed, whats the standard distance for BC's listed?

 

[wildgene]

Will a 150gr .277" BT be better than a faster 130gr FB for bucking wind? Is BC all that matters just for ballistics (not terminal ballistic). You never know what direction the wind will be when you have a shot. Head wind 10degrees 20degrees 180 degrees etc. Seems to me momentum has to come into play and sometimes slower heavier bullets have more of it.

Lag time is the only thing that affects amount of wind drift. That is the actual flight time to target minus what the flight time would be in a vacuum. Momentum has no effect on this value. BC does. The only reason a slower, heavier bullet can drift less is if it has a significantly higher B.C. The direction of the wind makes no difference in terms of which bullet will fair better.

...something about this statement makes me wonder. Obviously, the longer the ToF the more effect wind will have on a bullet, but, taking two 8mm bullets...

220gr. Sierra GameKing BC= 0.524/ SD= 0.301 @ 2800fps MV// 500yds. Tof= 0.614/ WD*=13.7"
200gr. Nosler Partition BC= 0.450/ SD= 0.274 @ 2900fps MV// 500yds. ToF= 0.611/ WD*=16.4"
(* Wind drift 10mph @ 3 o'clock full value)

...it would seem there's more happening here than just the duration of the flight, air resistance, or in our case lack thereof, or BC & momentum, a lighter bullet is easier to move, are both factors.

 

[tjen]

Thanks all, other than my 22 center fires I am pretty safe 250 yards is the longest shot I have choosen to take to date. My long range rifle is a 270win and I am working on 140gr AB loads for it with 140gr PT's as back up if the rifle perfers them.

In Mi I where I hunt its rare to shoot over 150-200 yards so my 270win has been neglected with my verious 35 cals answering the call.

 

[ROVERT]

...it would seem there's more happening here than just the duration of the flight, air resistance, or in our case lack thereof, or BC & momentum, a lighter bullet is easier to move, are both factors.

The lighter bullet is not easier to move. At least not from the winds point of view. The reason being that the heavier bullet also as proportionately more surface area exposed to the wind.

It really does come down to just flight time, which is purely a function of muzzle velocity and ballistic coefficient. The mass of the bullet is not important.

 

[Desert Fox]

...something about this statement makes me wonder. Obviously, the longer the ToF the more effect wind will have on a bullet, but, taking two 8mm bullets...

220gr. Sierra GameKing BC= 0.524/ SD= 0.301 @ 2800fps MV// 500yds. Tof= 0.614/ WD*=13.7"
200gr. Nosler Partition BC= 0.450/ SD= 0.274 @ 2900fps MV// 500yds. ToF= 0.611/ WD*=16.4"
(* Wind drift 10mph @ 3 o'clock full value)

...it would seem there's more happening here than just the duration of the flight, air resistance, or in our case lack thereof, or BC & momentum, a lighter bullet is easier to move, are both factors.

You are right in your assessment Wildgene. There's more to it,

Momentum, BC, TOF, Bullet design, velocity have all the contributing factor in the bullet ability to buck the wind. As I alluded in my previous post, if all else being equal, a heavy bullet with moderate speed will have less deflection than a lighter bullet with higher velocity. The data of two 8MM bullet you posted are a good example.

 

[tjen]

A body in motion whats to stay in motion untill acted opon by other forces. Is it correct to say a medium in this case air acts differently on bullets verying by (the bullets) velocity?

 

[Guy Miner]

tjen - maybe it's just me, I've only had one cup of coffee so far today, but I really can't follow... Nor figure out where you're going with this.

Long range rifle shooting is best done with a high BC bullet. It's a fascinating thing, and I've been doing mid-long range shooting for decades - but I can't quite follow where you're going with your questions & statements.

My apologies. Guy

 

[tjen]

Call it the belly smacker effect. More velocity produces more resistance in water thus it has more effect on whats moving thur it. Air is what 800 times linner than water but would not the same princables apply?

The example of the two 8mm bullets is a bit reveling. ToF and BC are the two biggest veriables and the easiest to control.

You call it a mute subject if you don't shoot over 200 yards or use pointed bullets out to 400 yards or sectect a high BC bullet if shooting over 400 yards.

 

[ROVERT]

...something about this statement makes me wonder. Obviously, the longer the ToF the more effect wind will have on a bullet, but, taking two 8mm bullets...

220gr. Sierra GameKing BC= 0.524/ SD= 0.301 @ 2800fps MV// 500yds. Tof= 0.614/ WD*=13.7"
200gr. Nosler Partition BC= 0.450/ SD= 0.274 @ 2900fps MV// 500yds. ToF= 0.611/ WD*=16.4"
(* Wind drift 10mph @ 3 o'clock full value)

...it would seem there's more happening here than just the duration of the flight, air resistance, or in our case lack thereof, or BC & momentum, a lighter bullet is easier to move, are both factors.

You are right in your assessment Wildgene. There's more to it,

Momentum, BC, TOF, Bullet design, velocity have all the contributing factor in the bullet ability to buck the wind. As I alluded in my previous post, if all else being equal, a heavy bullet with moderate speed will have less deflection than a lighter bullet with higher velocity. The data of two 8MM bullet you posted are a good example.

Here are calculations for wind drift for the chosen 8mm bullets.

I used the published B.C. values from the respective manufacturers at a range of 500 yds. The B.C. Gene used for the NPT is not what Nosler lists. When I run the numbers through JBM ballistics calculator, I get 21.6" wind drift with the 200 PT at 500 yds and 18.2" wind drift with the 220 SGK at 500 yds.

The numbers Gene used provide different ToF than what I got from JBM. It is irrelevant though. If you plug Gene's numbers into the formula I provided you get 13.8" drift for the 220 gr. and 16.6" for the 200 gr. As you can see from the numbers, lag time is the key to wind drift.

 

[Desert Fox]

Hmmm! So, the 220 is slower than the 200 therefore has longer TOF but deflect less.

Rovert, I'm confused