Less wind drift - heavier weight or more speed?

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Smitty8141

Smitty8141

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Oct 6, 2020
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New Jersey, United States
Here is a question I have had a difficult time answering with my shooting. Using the same power plant, same style projectile (pellet, slug), does a heavier projectile get pushed less by the wind than a lighter one traveling faster. It was always my belief that more weight helped buck the wind, but have seen on a few occasions where higher velocity seemed to help. Those times might have been a fluke, just seeing if anyone has seen this or was it just a wind change I didn't notice.
 
In general, heavier is better. I did an experiment with Strelok Pro comparing two pellets.

CP Pointed at 7.4 gr with a bc of .012

Pile Driver at 30. gr with a bc of .083

Range of 30 yards with a wind of 20 mph at 90 degrees

Pellet. Muzzle Velocity. Wind offset (inches)

CP Pointed. 500 fps. 10.6 in.

Pile Driver. 500 fps. 1.4 in.

CP Pointed. 1000 fps. 6.7 in

Pile Driver. 1000 fps. 1.1 in

This experiment uses pellets of a very great difference in weight. But the effect is pretty clear. As the weights of the pellets converge the differences would be less.


 
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Don't think of wind as being wind. At the exact time you fire, think of it as a fixed snapshot of a three dimensional pressure gradient (higher resistance on one side, lower resistance on the opposing side, and not in a linear fashion—it's always changing throughout the snapshot) that the projectile must pass through. All other things being equal, a projectile with a higher inertial mass will be less affected by this external pressure gradient than a projectile with a lower inertial mass, since the higher inertial mass allows it to be more resistant to changes in acceleration—in this case, the "side-to-side" forces of that 3D pressure gradient that the projectile is passing through.
 
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Don't think of wind as being wind. At the exact time you fire, think of it as a fixed snapshot of a three dimensional pressure gradient (higher resistance on one side, lower resistance on the opposing side, and not in a linear fashion—it's always changing throughout the snapshot) that the projectile must pass through. All other things being equal, a projectile with a higher inertial mass will be less affected by this external pressure gradient than a projectile with a lower inertial mass, since the higher inertial mass allows it to be more resistant to changes in acceleration—in this case, the "side-to-side" forces of that 3D pressure gradient that the projectile is passing through.
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haha. this may be true, but i’m gonna still call it wind.
 
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I think that’s generally true with the slugs that we shoot from our air rifles. However, it’s certainly not true with the pellets we shoot. Look at the below from JSB:

Pellet BC Weight

.22 RD Monster. 0.053 25.4 grains

.25 King Heavy Mi2. 0.054 33.95 grains 

.30 Exact. 0.042 44.75 grains

.35 Exact. 0.045 81 grains

As you can see the two lighter pellets have a significantly better BC…
 
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Just don't forget from this link:

https://www.airgunnation.com/topic/what-is-ballistic-coefficient/

"...BCs change with velocity, so a listed BC of a bullet or a pellet is only really meaningful if you know at what velocity the projectile was measured. Bullets tend to have a better BC the faster they are going and a worse BC as they begin to slow down, but a pellet’s BC is generally the opposite. A pellet is going to slow down a lot faster in the 1000-800 fps range, and thus have a worse BC than it will in the 600-400 fps range."

I believe it was Bryan Litz in Applied Ballistics For Long-Range Shooting that at least hypothesized that a faster, lighter bullet maybe affected less by wind simply because of the speed. That statement goes against many other experts, and I have no idea if it even applies to pellets :p
 
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Just don't forget from this link:

https://www.airgunnation.com/topic/what-is-ballistic-coefficient/

"...BCs change with velocity, so a listed BC of a bullet or a pellet is only really meaningful if you know at what velocity the projectile was measured. Bullets tend to have a better BC the faster they are going and a worse BC as they begin to slow down, but a pellet’s BC is generally the opposite. A pellet is going to slow down a lot faster in the 1000-800 fps range, and thus have a worse BC than it will in the 600-400 fps range."

I believe it was Bryan Litz in Applied Ballistics For Long-Range Shooting that at least hypothesized that a faster, lighter bullet maybe affected less by wind simply because of the speed. That statement goes against many other experts, and I have no idea if it even applies to pellets :p
Click to expand...

He was talking more in supersonic terms.
 
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Well, here's some thoughts from recent experimenting with two weights of pellets. All of this in .22 cal.

JSB 18.13 at 940-950fps for about 35fpe shot very good, BUT really sucked in the wind. No wind, or light winds, and this combo would shoot really well. But any wind and it was taking that 18.13grainer for a ride. 

JSB 25.39 at 850-860 for about 41fpe. Also a very accurate barrel/pellet/speed/etc combo. Wind is pushing this projectile much much much less. 

At first glance a guy would think that the 18.13 is going so much faster that it would have much less time to be affected by the wind.......but, that lighter pellet has a much poorer BC, so strips its speed faster. 

The BCs that I collected from this particular gun are relevant and interesting so here they are: 18.13gr @ 940.5fpe = 0.034 and 25.39 @ 850 = 0.049.

Legacy version of Chairgun says it takes the 18.13 @940 with a BC of 0.034, 0.356 seconds to go 100 yards and takes the 25.39 @ 850 with a BC of 0.049, 0.380 seconds to travel 100 yards. So, even though the lighter/faster pellet started out going almost 100fps faster than the heavy/slow one, by 100 yards the light one has been stripped of its speed so much that it isn't traveling much faster than the heavy one. 

Chairgun says the 25.39 @ muzzle velocity of 850 will be doing 734.2fps at 100 yards (86.4% of its starting velocity) and the 18.13 @ muzzle velocity of 940 will be doing......758.8fps at 100 yards (80.7% of its starting velocity). Ballistic coefficient in effect. Stretch out the distance much further and that 25.39grainer with the better BC is going to overtake the 18.13 in speed. 

Ballistic modeling info is fun, but real-world data is showing the same thing as I test these two configurations out. 


 
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Here is a question I have had a difficult time answering with my shooting. Using the same power plant, same style projectile (pellet, slug), does a heavier projectile get pushed less by the wind than a lighter one traveling faster. It was always my belief that more weight helped buck the wind, but have seen on a few occasions where higher velocity seemed to help. Those times might have been a fluke, just seeing if anyone has seen this or was it just a wind change I didn't notice.
Click to expand...


For pellets (not slugs) in general round nosed slugs tend to perform best in the 800 to 900 fps range. Above about 870 fps they shed velocity so fast that the additional speed does not translate to much additional velocity down range.

Slugs are a completely different ball of wax. One might be able to launch them at supersonic velocities but they (in airguns) do not have the sectional density to fly well in that velocity range. They certainly do perform better than pellets at velocities above 900 fps, but they can also out perform pellets below that velocity because of their better form factors. Slugs probably should not be modeled using the GA drag model (Sterne would be a good source to check with on that assertion before taking my word.). I would think the G1 drag model would be better for modeling most airgun slugs.

In short, you are making a trade off between the ability of the light pellet to "penetrate" the air and the ability of your rifle to accelerate the heavy pellet to comparable velocities. Sometimes the one situation will prevail, sometimes the other will.

Chairgun has a nice feature that lets you compare the ballistics models of up to four different projectiles at the same time.
 
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This was copied from Franklink’s post

Chairgun says the 25.39 @ muzzle velocity of 850 will be doing 734.2fps at 100 yards (86.4% of its starting velocity) and the 18.13 @ muzzle velocity of 940 will be doing……758.8fps at 100 yards (80.7% of its starting velocity). Ballistic coefficient in effect. Stretch out the distance much further and that 25.39grainer with the better BC is going to overtake the 18.13 in speed. 


That really shows the difference BC has on what we shoot. If your shooting 100 yards or farther, it seems BC is more important than initial velocity considering the pellet shoots well at that speed. Good info.


 
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Here is a question I have had a difficult time answering with my shooting. Using the same power plant, same style projectile (pellet, slug), does a heavier projectile get pushed less by the wind than a lighter one traveling faster. It was always my belief that more weight helped buck the wind, but have seen on a few occasions where higher velocity seemed to help. Those times might have been a fluke, just seeing if anyone has seen this or was it just a wind change I didn't notice.
Click to expand...


For pellets (not slugs) in general round nosed slugs tend to perform best in the 800 to 900 fps range. Above about 870 fps they shed velocity so fast that the additional speed does not translate to much additional velocity down range.

Slugs are a completely different ball of wax. One might be able to launch them at supersonic velocities but they (in airguns) do not have the sectional density to fly well in that velocity range. They certainly do perform better than pellets at velocities above 900 fps, but they can also out perform pellets below that velocity because of their better form factors. Slugs probably should not be modeled using the GA drag model (Sterne would be a good source to check with on that assertion before taking my word.). I would think the G1 drag model would be better for modeling most airgun slugs.

In short, you are making a trade off between the ability of the light pellet to "penetrate" the air and the ability of your rifle to accelerate the heavy pellet to comparable velocities. Sometimes the one situation will prevail, sometimes the other will.

Chairgun has a nice feature that lets you compare the ballistics models of up to four different projectiles at the same time.
Click to expand...

I use Strelok mostly for ballistic calculations. RA4 usually works best for all of the airgun slugs that I shoot regularly in 22 cal. It also worked well for some of the 30 cal NSAs that I have shot, but I had problems with it with the 65.5gr NSAs and 62gr Varmint Knockers, where G1 works best. These problems always manifested somewhere north of 125m.
 
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Don't think of wind as being wind. At the exact time you fire, think of it as a fixed snapshot of a three dimensional pressure gradient (higher resistance on one side, lower resistance on the opposing side, and not in a linear fashion—it's always changing throughout the snapshot) that the projectile must pass through. All other things being equal, a projectile with a higher inertial mass will be less affected by this external pressure gradient than a projectile with a lower inertial mass, since the higher inertial mass allows it to be more resistant to changes in acceleration—in this case, the "side-to-side" forces of that 3D pressure gradient that the projectile is passing through.
Click to expand...

No,,,,do think of it as wind and think of the side profile of the pellet as the surface against which the wind blows, While we commonly refer to ballistic coefficients, they are generated by the tip profile and the air around them whereas wind drift is generated by the side profile and the wind against it. There are some similarities of the two numbers because they partly are function of the mass of the pellet, or slug. however the side profiles are quite different for some equal weight projectiles and do also determine wind drift. You probaly could calculate a ballistic coefficient for a side winded drift , assuming that the wind force is acting similar to gravity
 
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