Range Report Do lighter bullets suffer from wind significantly more than heavy bullets?

[garandman]

Say, 6.5 CM vs. 338LM?

I know conventional widsom / theoretical analysis says "Yes" but the lighter / smaller bullets also has a smaller profile for wind to catch.

Anyone with any personal experience with light vs. heavy bullets can give actual numbers? Say at 500+ yds?

Thx.

 

[Temp9]

Your ballistic coefficient will tell you everything you need to know about how a bullet cuts through the wind.

 

[garandman]

Your ballistic coefficient will tell you everything you need to know about how a bullet cuts through the wind.

Will it tell me how it will do for a 90 degree full value 15 mph wind? Perhaps I wasn't clear above. That's what I'm wanting to know.

And I realize I really just need to go try it, but I was curious about others experiences.

 

[Niles Coyote]

JBM - Calculations - Trajectory (Simplified)

yes

 

[Temp9]

In a 15mph full value wind, the air will hit the bullet at about .4 degrees off axis. The BC for the bullet won't change any detectable amount just because there is wind. That's why we bother with finding a BC at all.

 

[excaliber]

BC varies with velocity. Example, a 308 shooting a 208 A-max (BC is .648) isn`t exactly that at the slow velocity a 308 pushes it. Now a 308 shooting a 168gr Berger Hybrid,BC is .519, at 308 velocity, will outperform the AMAX by quite a bit. There comes a time when velocity will beat BC. Check out Bryan Litz book, Applied Ballistics.

 

[BoilerUP]

BC varies with velocity. Example, a 308 shooting a 208 A-max (BC is .648) isn`t exactly that at the slow velocity a 308 pushes it. Now a 308 shooting a 168gr Berger Hybrid,BC is .519, at 308 velocity, will outperform the AMAX by quite a bit. There comes a time when velocity will beat BC. Check out Bryan Litz book, Applied Ballistics.

Using Litz G7s, the 208 can be over 400fps slower than the 168 Hybrid and it STILL beats it in wind drift.

 

[40xs]

To better figure out that answer watch what the winners are shooting. Every time I hear of someone trying lighter bullets it isn't long before you see them going back to the heavies. Early on in "F" class you would see all sorts of weights at matches. Truth is; the last several big matches the F/TR high placers and winners are shooting the 210-230 gr. bullets. Of course this requires rebarreling for the bullet changes. New records are being set and more "clean" (perfect) scores are being turned in with the heavies. You be the judge! Light bullets still rock on "blue bird" relays where there is no wind, but find relays where there is no wind. lol.

 

[Aimsmall55]

Using Litz G7s, the 208 can be over 400fps slower than the 168 Hybrid and it STILL beats it in wind drift.

Not to mention shoot FARTHER... and hit HARDER

 

[shooter.dm]

In order to get better peformance from a lower bc your velocity must be 200 fps fatster per .1 bc the 168 hybrid will out perform the 208 as long as the fps is some were around 230 fps faster all day long

 

[260shooter]

From what i've seen and heard about in F-Class (open) the 6.5X284 was the Belle of the Ball for quite some time, it might still be I don't follow it closely anymore. But, at one point people started shooting the straight 284 with heavier 168-180 gr projos. I was told even if they are equal in wind, with some types of wind (head or tail wind) the heavier bullet will give smaller vertical speads. Lets use a 1K hi-power range. When firing at 1K with a head wind, that wind hits a firing berm closer in, say at 600 yards. The wind hits that berm and deflects up causing an up draft that you can't see. If it is steady, no problem, you take a click or two out of elevation and your back in the X. If it's a variable head wind, lets say your first 5 shots are X's the wind picks up and you shoot a high 9 and you adjust for it, then the head wind dies down after two shots and you get a low 9. anyway you get my point, you are chacing the wind only in a different direction up and down. The heavier bullets ride through this condition better than lighter ones.

 

[shooter.dm]

The one and only thing that matters is the bc two bullets with the same bc fly and react to the wind exactly the same no matter size or weight

 

[BoilerUP]

the 168 hybrid will out perform the 208 as long as the fps is some were around 230 fps faster all day long

That's not what Litz G7s say in any ballistic calculator.

Again...the 208 has less wind drift than a 168 Hybrid, even going 400fps slower. ***EDIT*** Looking again, the 168H wins by a tenth of an inch or so to about 600yd, then the 208 with 400fps handicap matches it, and 700yd+ the 208 beats it in the wind.

 

[shooter.dm]

It looks like u are right

 

[garandman]

That's not what Litz G7s say in any ballistic calculator.

Again...the 208 has less wind drift than a 168 Hybrid, even going 400fps slower. ***EDIT*** Looking again, the 168H wins by a tenth of an inch or so to about 600yd, then the 208 with 400fps handicap matches it, and 700yd+ the 208 beats it in the wind.

That's the kind of info I'm looking for. Now, someone who has actually shot both...

 

[260shooter]

I shot the 168 in a 308 years ago. Wind really blew it around. Now I shoot the 208 A-MAX in a 300 Norma Mag at 3100 fps and the wind doesn't effect as much.

 

[CoryT]

Wind does not 'blow bullets around'. Wind drift is a function of drag, drag is represented by BC or Cd. Given equal velocity, a higher BC bullet will have less drift. Bullet size is not an issue, bullet mass and cross section correlate to BC, length and diameter do not.

Wind does not 'push' on the side of the bullet. The bullet turns into the relative wind and drifts downwind because of drag.

At some point, reducing the velocity of a bullet will produce more wind drift than a bullet with a lower BC at a higher velocity. This is why .308 shooters are not using 220 grain bullets or 90 grain bullets, since pressures don't allow for enough velocity It takes quite a bit of velocity change to overcome a BC advantage, and pressure for the cartridge limits you at the top and bottom end of effective bullet weights. In almost every case you will be better off with the higher BC bullet when it comes to wind drift.

Note that that may come with an elevation trade off. You may well get better wind performance, but increased drop, which then reduces the danger space. With laser range finders, ballistic computers and high precision scopes, danger space is much less of a problem than wind drift.

 

[waveslayer]

Know your BC, that will determine majority of the wind issues. Plus bullet weight, usually the heavier the better for longer range to kick the wind in a sense.

 

[VKC]

I shot my 6.5 Creedmoor vs my friend's 338LM out to 1000 yds and kept up with him without a problem. It all depended on target size, distance and most importantly wind calls.

Accurate velocity specified BC is what determines wind drift at a specified distance not the weight of the bullet.

However, kinetic energy is approximated by the formula of ½ mv² with m = mass and v = velocity. A heavier bullet will retain or lose less velocity than a light bullet at further varied distances.

 

[MontanaMarine]

I shoot some 155 Scenar, and 208 AMax in the 308 Win. In my experience with these two bullets, the 208 significantly outperforms the 155 in drift and energy. The 155 is a little flatter to 1K. But the 208 shoots pretty well out to 1500 yards or so.

I'm at 4500' ASL.


155 Scenar 2900 fps (shooting BC .465)

1K drop - 26.7 moa
1K drift - 6.2 moa
1K energy - 873 ft-lbs



208 AMax 2600 fps (shooting BC .630)

1K drop - 29.3 moa
1K drift - 4.7 moa
1K energy - 1306 ft-lbs

 

[jwp6114]

I shoot some 155 Scenar, and 208 AMax in the 308 Win. In my experience with these two bullets, the 208 significantly outperforms the 155 in drift and energy. The 155 is a little flatter to 1K. But the 208 shoots pretty well out to 1500 yards or so.

I'm at 4500' ASL.


155 Scenar 2900 fps (shooting BC .465)

1K drop - 26.7 moa
1K drift - 6.2 moa
1K energy - 873 ft-lbs



208 AMax 2600 fps (shooting BC .630)

1K drop - 29.3 moa
1K drift - 4.7 moa
1K energy - 1306 ft-lbs

how much barrel, and what powder combination do you need to get the 208 up to 2600 from a 308?

 

[turbo54]

The physics models say two bullets, regardless of their weight, will have identical trajectory and wind drift if the have the same BC and MV.

my gut tells me this is nearly true, but it sure seems to me the heavier bullet still has the advantage. Completely unscientific, and against what the latest/greatest physics models predict. Just what I "feel" I've seen and experienced shooting various bullets from various cartridges.

 

[MontanaMarine]

how much barrel, and what powder combination do you need to get the 208 up to 2600 from a 308?

22" bbl (Rem 700 SPS Varmint, factory twist/throat).
49.0 gr RL17
Moly'd 208 AMax
Win brass
CCI 200 primer
3.08" OAL.

This load actually chrono'd 2670 fps from the 26" bbl. I cut it to 22" and it is now chrono'ing at 2620 fps.

 

[40xs]

There is a tremendous amount of science behind all of this discussion, plus a lot of good theory. But looking at it from a very elementary and ancient viewpoint, imagine a blowgun shooting either a 3 inch plastic dart verses a 3 inch steel dart of the same diameter at a target; which one is going to be most reliable shot after shot in a little wind???

 

[damoncali]

The weight cancels itself out in the math used to calculate the drag. But BC is not totally independent of weight - it has units of pounds/in^2 - the same as sectional density, which is why we intuitively feel heavy bullets are better. But that is because weight is already baked into the BC.

 

[tobias]

The weight cancels itself out in the math used to calculate the drag.

That's completely wrong. Drag force is independent of mass, therefore it cannot cancel out.

Wind drift depends on lag time. With a higher mass lag time becomes smaller, provided all other variables held constant! The problem is, that you can't hold all other variables constant, but mostly a bullet with a higher mass has less wind drift for longer range.

 

[damoncali]

That's completely wrong. Drag force is independent of mass, therefore it cannot cancel out.

Wind drift depends on lag time. With a higher mass lag time becomes smaller, provided all other variables held constant! The problem is, that you can't hold all other variables constant, but mostly a bullet with a higher mass has less wind drift for longer range.

Hence the "weight is baked into BC", which does not cancel itself out. I don't think you disagree with me.

 

[pawprint2]

The one and only thing that matters is the bc two bullets with the same bc fly and react to the wind exactly the same no matter size or weight

Not as easy as it sounds. Outside of the "theoretical" there are a couple of small things that actually effect a given round. Safe chamber pressure, and case capacity come to mind. It is usually possible to fire a lighter projectile from a given rifle faster than a heavier projectile. I said usually, obviously there are going to be times this is not true, type of bullet, bearing surface etc. will have a big effect on mv. Therefore, generally speaking a lighter bullet can be fired faster than a heavier bullet, therein lays the rub. There is an interesting article on Accurateshooter.com regarding the heavier bullet "always has less wind drift". When you look at the table of bullets in the test, and the drift, you can see this is Not true. It may be true that the lowest drift was the heaviest bullet tested, but between all the bullets tested, some of the lighter bullets had less drift than some of the heavier bullets. The common practice of tipping a bullet, with a good tipping die, such as the Widden, increases BC without adding weight. In fact if you trim prior to tipping, you will actually end up with a higher than original BC with a lighter bullet, due to the trimming. I have seen and read, even on this board, various "experts" claim the heavier bullet always has a better BC! Of course, they don't get out much. Bullet shape and density of material have a lot to do with things, not SD, but true material density. Tungsten bullets, vs copper jacketed lead core vs homogenous copper vs multi sectional-such as military penetrators, HE, HEI etc. have great variations in length and surface are, any given cross section has a density, but if the weight of the projectile and the caliber is known, regardless of what it is made of, will have the same SD as long a the two weight are constant. You can and do get diminishing returns as the bullet gets heavier and heavier, it will necessarily start to have slower and slower MV.

 

[shooter.dm]

All the info I'm getting is from Brian Litz and I thank he know more then we do

 

[damoncali]

All the info I'm getting is from Brian Litz and I thank he know more then we do

You're right. You just left out "all else equal".

What seems to be getting lost is that BC is a function of bullet weight. To to say "only BC matters" is to say "weight matters". But weight does not matter at all once you've decided you are going to use BC in your math, because it's already figured in.

 

[shooter.dm]

You are correct

 

[pawprint2]

You're right. You just left out "all else equal".

What seems to be getting lost is that BC is a function of bullet weight. To to say "only BC matters" is to say "weight matters". But weight does not matter at all once you've decided you are going to use BC in your math, because it's already figured in.

I agree 100%, the weight and the SHAPE are taken into account, I'd like to add, that the BC of a given projectile also is not static, the BC has a range based on velocity, and it is not linear, nor does it always increase with velocity. You'd be amazed at how many people, ( some on this very board) will argue- that the heavier bullet always has a higher BC, regardless of shape or Velocity-but that's life.

 

[shooter.dm]

What I was trying to say from the beginning is that a heavier bullet is not allways better than the lighter bullets as every one is claiming it is

 

[gstaylorg]

What I was trying to say from the beginning is that a heavier bullet is not allways better than the lighter bullets as every one is claiming it is

As has been hashed out above, this is true if, and only if, you can push them enough faster than the heavier projectile to overcome the the ballistic disadvantage usually found when comparing lighter modern projectiles to heavier. However, in a practical sense, that may not be so easy to do depending on the specific caliber/case volume/powder, etc. As an example, look at .308 Berger 155.5s versus Berger 185 gr Juggernauts. Using JBM Ballistics predictions, the 155.5s at 3000 fps MV would have a deflection of 8.1 MOA at 1000 yd due to a full-value 10 mph crosswind. The 185s at 2800 fps would have a deflection of 7.1 MOA. That's a significant difference at 1000 yd. Depending on the disparity in BC between light/heavy, maybe the difference won't show up in the noise at close range, but it's still there. Both those MVs are readily achievable with each projectile. However, trying to push the lighter projectile fast enough to overcome the ballistic disadvantage of the heavier (3250 fps is about where the 155.5 would catch up to the 185s on paper) would be difficult, if not impossible, for most. It would almost certainly be unsafe, even if reachable, whereas 2800 fps for the 185 Juggernaut can be readily achieved. So even though the lighter projectiles can be made to at least equal the performance of the heavier in theory, in reality it usually isn't practical to do so.

 

[pawprint2]

A very good article regarding WD and bullet weight was written by German Salazar (working with Bob Jensen) and can be found on Accurateshooter.com, the following table was compiled with data from a 30-06@ 60,000psi:


Below is a chart showing the six bullets tested, the muzzle velocity attained with each at 60,000 psi chamber pressure, the remaining velocity at 1000 yards, and the calculated wind drift at 1000 yards. 1000-yard velocities and drift numbers are calculated using each manufacturer’s advertised ballistic coefficient. While this may not provide a perfect comparison across brands, it is certainly a valid method for brand-specific comparisons as the same methodology is used to calculate each brand’s BC.

Bullet Muzzle Velocity (fps) 1000-Yard Velocity (fps) Percentage of MV Retained at 1000 Yards Wind Drift at 1000 Yards (inches)
Sierra 190 MK 2820 fps 1472 fps 52.2% 73.0″
Sierra 200 MK 2760 fps 1498 fps 54.3% 69.7″
Lapua 185 D46 2880 fps 1548 fps 53.8% 67.9″
Berger 175 2980 fps 1593 fps 53.5% 66.2″
Berger 185 2900 fps 1605 fps 55.3% 63.6″
Berger 210 2730 fps 1611 fps 59.0% 59.2″
As you can see from this table, the berger 185 has 6.1 less wind drift than the Sierra 200 MK, the lighter berger 175 and the Lapua 185 had less. It is true the Berger 210 had the least, and it was the heaviest bullet tested, but a blanket statement regarding windrift and weight, is false, experts conducting first class testing have demonstrated this many times. I've always been partial to the old D46 in a 3006, it has served me well, but after reading this article I ordered some berger 185's (they are still unloaded as I have other projects as we all do waiting their turn). If any of you get a chance, go over to Accurateshooter.com and read the article-very interesting. German Salazar is a wealth of knowledge, as are those he shoots with.

 

[turbo54]

Two words:

FORM FACTOR

 

[40xs]

As I understand it, B.C. is the sum value of all the other factors figured in. Now ruling out all the older less competitive bullets that may still be on the market and evaluating only the ones now used in comps. we can cut to the chase and say that it is going to be very difficult to design a 155gr. bullet with the b.c. of a 215-230gr. already designed for long range comps for the purpose of defeating wind problems. Obviously, in order to glean the desired results from such overly heavy bullets for caliber ( .308 ) one will need extended lead space to the lands to allow the bullet to be seated out far enough as to not eat up valuable powder space and to give adequate velocity to capitalize on the intended extra benefits of the longer, heavier bullet. So, If one is attempting to use a heavy, high b.c. projectile in a stock, unaltered .308 chamber they will most likely be disappointed in their results due to inadequate velocity ( which is necessary for the b.c. qualities ) and will be better served using a bullet in the midrange of around 185gr. Also, a tighter twist is mandatory to stabilize the longer bullet, which also means a new barrel. I've shot f/class for ten years and used everything available in my .308's. This is how I see it!!!

 

[MontanaMarine]

What I was trying to say from the beginning is that a heavier bullet is not allways better than the lighter bullets as every one is claiming it is

Maybe if you compare a light VLD to a slightly heavier SMK, flat base, or round nose bullet.

If you compare similar bullet designs (VLD to VLD, or SMK to SMK, etc), it's tough to cite a real world example where light beats heavier in the wind, from the same chambering.

 

[40xs]

Unless the real world experience is seeing who is taking home the gold and who is going home and ordering new bullets. Proof in the pudding.

 

[MontanaMarine]

I send enough light and heavy bullets downrange to 1000+ via 308 Win to have a clear picture of which one cheats the wind better. The results speak for themself. No trophy necessary.

Pass the 208s, 210s, 215s, and 225s. Keep the lightweights.