Author Topic: Can someone explain how heavier pellets "buck the wind" better?  (Read 1055 times)

rsterne

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #15 on: July 14, 2018, 09:35:56 AM »
I can give you a good example of where the "heavy pellets are better" idea comes from....

Go to the HAM BC chart, scroll down to .22 cal, and type "jsb exact" in the box in the search box, upper right.... You are now looking only at a family of pellets of similar shape, all of the same diameter....

Now sort by weight (or SD), and look at the BCs.... you will find that the heaviest pellets have the higher BCs....

It is absolutely true that the lower wind drift is due to a higher BC, not a greater weight.... HOWEVER, that higher BC is due to the greater weight....  8)

If you compare similar weights and shapes in different calibers, then in fact the smaller caliber (which has the higher SD) will usually have a better BC, and therefore less wind drift.... If you replace the word "weight" in the old adage with "SD", then it makes (almost) perfect sense.... and larger calibers TEND to have higher SDs because of the square-cube rule.... 2 times the diameter is 4 times the area but 8 times the weight.... which doubles the SD.... This means that larger calibers have an advantage in SD, and therefore a potential advantage in BC, if the shapes (FF) are similar....

Bob
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Harpoon1

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #16 on: July 14, 2018, 09:48:34 AM »
Quote
.....It is absolutely true that the lower wind drift is due to a higher BC, not a greater weight....

If you would have only said that to begin with! 8)

Thanks Bob!
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Motorhead

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Re: Can someone explain how heavier pellets "buck the wind" bette
« Reply #17 on: July 14, 2018, 09:49:36 AM »
I live in the real world and SHOOT COMPETITIVELY ..... my experience is hands on real world.
While math and data for most rule the day, for me I take results at face value in spite sometimes to what the data may say.

I'm old school learning from doing ... so right or wrong in eyes of others it really don't sway me much.

This is the internet and we all are just sharing life experience & belief in what were doing.
Ones success can be weighted / connected somewhat to what you think you know ... I'm doing just fine  8)

Scott

Im not here to argue with you, to the contrary, Im here trying to get answers. Its not personal, at least for me it isn't. Frankly, you've foregotten more about airguns then I'll ever know. Having said that, I still cant reconcile why the ballistic apps come to a different conclusion.

I'm not here to argue or defend my thought either  ;)
What is different in AIR GUNS to Powder Burner ballistic data is that we shoot SO MUCH SLOWER and time to target and effects wind has on us so vastly different.  Add to the post Bob made in Correcting my statement ( Speed loss being so amplified over distance )

Yes my statement based upon equal caliber ( So frontal area created drag is nearly the same ) but the mass/weight of projectile differs.

What I'm eluding too is, if you visualize it in this manor ... is that the pellet Point A to Point B is moving threw open air where the air density in unchanged. The projectiles forward motion we really don't want to look at because we're ONLY looking at the area of the projectile as seen ( For this discussion ) by the cross wind lets say 90* to the projectile forward motion.
As stated earlier the weight/mass of the projectile and the wind if looked at as a constant speed  hitting it from a 90* angle will attempt to move the projectile in the direction the wind is blowing.
Lighter the weight of projectile greater will be it's trend to move with the wind ... greater the weight less it will move.  Where the RATIO statement was made in that the wind exerts a certain amount of it's energy into said projectile and where you see this wind drift issue difference light to heavy with projectile.

That was / is my intent to contribute to this conversation and IMO a contributing reason why heavier "Bucks the wind better" hoping to keep it somewhat simple in explanation.

There is a WHOLE LOT more going on and the cause & effect I'm speaking of is just a small piece of the much larger puzzle.
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Alan

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #18 on: July 14, 2018, 09:58:09 AM »
Ah, to we think we're dealing with absolutes! And we are, as long as we're using the same set of definitions! Where things really get complicated is in defining terminal ballistics, where nothing is "absolute"!!

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rsterne

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #19 on: July 14, 2018, 11:04:08 AM »
Actually, if you look a the whole statement, and not just the first half.... and remembering that the comparison was for pellets of the same caliber and approximate shape....

Quote
It is absolutely true that the lower wind drift is due to a higher BC, not a greater weight.... HOWEVER, that higher BC is due to the greater weight....

Since if A = B and B = C, then A = C.... it would follow that greater weight would result in lower wind drift.... (providing caliber, shape and velocity are constant)  ;)

Kind of like the science of Statistics....

Statistics are like a bikini.... what they reveal is enticing, but what they conceal is vital....  ::) 8) :o

Bob
« Last Edit: July 14, 2018, 11:05:44 AM by rsterne »
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Harpoon1

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #20 on: July 14, 2018, 11:15:48 AM »
Actually, if you look a the whole statement, and not just the first half.... and remembering that the comparison was for pellets of the same caliber and approximate shape....

Quote
It is absolutely true that the lower wind drift is due to a higher BC, not a greater weight.... HOWEVER, that higher BC is due to the greater weight....

Since if A = B and B = C, then A = C.... it would follow that greater weight would result in lower wind drift.... (providing caliber, shape and velocity are constant)  ;)

Kind of like the science of Statistics....

Statistics are like a bikini.... what they reveal is enticing, but what they conceal is vital....  ::) 8) :o

Bob

I took "just the first half" because that was the relevant answer to the question I asked.   ;D

The second part of the statement was akin to  "moving the goal post" on me. Same caliber but different weight,  would change the BC/SD between the pellets. The controls for my example were,  "All things being equal, like velocity and BC/SD"...... 8)
« Last Edit: July 14, 2018, 11:21:20 AM by Harpoon1 »
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rsterne

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #21 on: July 14, 2018, 11:24:48 AM »
Perhaps we should put more emphasis on this part of your original post....

Quote
So, in broad general terms it would seem, the faster the projectile, along with factoring in it's BC, the less time the projectile is effected by the wind, i.e. the less deflection?

Pick any BC you want, and any range, and any wind direction and speed, and calculate the wind drift with a muzzle velocity of 800 fps....

Double the velocity to 1600 fps, and see what happens to the drift.... It certainly is not half as much, as the original hypothesis would suggest.... In fact, it turns out to be about 30-60% greater (depends on BC and range chosen).... This is because the Cd is much greater when Supersonic, so even though the time of flight is shorter, the "lag time" is greater....

Bob
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Harpoon1

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #22 on: July 14, 2018, 12:05:33 PM »
Well to be honest, I just assumed we would stick to "normal" airgun speeds, and/or at the very least stay subsonic.  ;D





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rsterne

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #23 on: July 14, 2018, 12:19:39 PM »
Normal airgun speeds.... A JSB 18.3 gr. Heavy at 50 yards, and Subsonic....



As you can see, faster isn't necessarily better.... The chart was calculated using ChairGun….

Bob
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Harpoon1

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #24 on: July 14, 2018, 12:56:43 PM »
Normal airgun speeds.... A JSB 18.3 gr. Heavy at 50 yards, and Subsonic....



As you can see, faster isn't necessarily better.... The chart was calculated using ChairGun….

Bob

Yessir, I see that.  ;D

Would using heavier pellets mean less deflection?
« Last Edit: July 14, 2018, 01:39:13 PM by Harpoon1 »
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rsterne

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #25 on: July 14, 2018, 02:02:10 PM »
If they were the same shape and caliber (ie Cd), yes, because the SD would be higher.... The entire curve would move downwards on the graph....

Another example would be three identical pellets, made of aluminum, tin, and lead.... The heavier pellet would have a higher SD, but the drag at any velocity would be the same.... The lead pellets would slow less, having a smaller "lag time", so therefore less wind drift.... The aluminum pellet would drift the most....

Bob
« Last Edit: July 14, 2018, 02:03:41 PM by rsterne »
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Harpoon1

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #26 on: July 14, 2018, 03:00:20 PM »
If they were the same shape and caliber (ie Cd), yes, because the SD would be higher.... The entire curve would move downwards on the graph....

Another example would be three identical pellets, made of aluminum, tin, and lead.... The heavier pellet would have a higher SD, but the drag at any velocity would be the same.... The lead pellets would slow less, having a smaller "lag time", so therefore less wind drift.... The aluminum pellet would drift the most....

Bob

Bob,

Got it, thanks.

Last question, if I may?

Comparing an 8 grn .177 and 16 grn .22, common weights for their repsective calibers. Lets assume, hypothetically of course,  both have the same BC/SD and the same velocity, say 850 fps.  Would one pellet experience/be subject to, more or less wind deflection than the other?

Thanks.




« Last Edit: July 14, 2018, 03:30:27 PM by Harpoon1 »
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rsterne

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #27 on: July 14, 2018, 04:35:25 PM »
The SD of the 8 gr. .177 cal is 8/7000/.177/.177 = 0.0365

The SD of the 16 gr. .22 cal is 16/7000/.22/.22 = 0.0472

If the shape was identical, at the same velocity the .22 cal should have a better BC and less wind drift.... If I didn't have a BC available for them, and they were JSB Exacts, I would use (0.0365 / 1.5) = 0.024 for the BC for the .177 and (0.0472 / 1.5) = 0.031 for the BC for the .22 cal....

Bob

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Harpoon1

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #28 on: July 15, 2018, 01:47:36 PM »
The SD of the 8 gr. .177 cal is 8/7000/.177/.177 = 0.0365

The SD of the 16 gr. .22 cal is 16/7000/.22/.22 = 0.0472

If the shape was identical, at the same velocity the .22 cal should have a better BC and less wind drift.... If I didn't have a BC available for them, and they were JSB Exacts, I would use (0.0365 / 1.5) = 0.024 for the BC for the .177 and (0.0472 / 1.5) = 0.031 for the BC for the .22 cal....

Bob

Huh?

Thats not what I asked?

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Gerard

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Re: Can someone explain how heavier pellets "buck the wind" better?
« Reply #29 on: July 15, 2018, 01:59:56 PM »
My sense is that Bob tried to offer a real-world type of answer, not based on what seems to be a fictional scenario in which a .177" and .22" pellet have the same BC. As BC is a function of both weight and size/shape, and since two pellets of profoundly different weights and sizes are what's in question, it doesn't seem rational to expect an identical BC for both, hypothetically or otherwise. But then maybe my lack of apprehension of the math involved is the problem? Perhaps you could explain with numbers how you're cooking up identical ballistic coefficients for two pellets, one larger than the other and weighing twice as much? It's no good pretending that they can have the same BC, because they just don't and probably can't.
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