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MaximumSmoke
PostPosted: Fri Jan 10, 2020 8:34 pm  Reply with quote
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His Masters was in Statistics which is how he made his living, and that is really all a shotgun pattern is, statistics.


1) Statistics is not Physics (believe me I know, check my credentials, it's how I made my living)
2) We're not talking statistics when we are talking about air density effects on pellet flight, we are talking about a physical effect, not a statistical one -- to wit, the air-flow interference, pellet-to-pellet, in a shot cloud.

The only use of statistics in shotguns is to quantify the repeatability characteristics of shotgun patterns and ballistics, both internal and external. We do not use statistics to examine pattern spread, which is the subject of the article's premise.

Let's be clear on the subject. The article proposes air density is a significant factor in pattern spread, and covers experiments to show that. But instead of air density, altitude is posited to be the factor of influence in the article. However, air density, while obviously depending on altitude, is also highly dependent on temperature. Further to the demonstration of that fact, we in Minnesota, for example, who live at 900 feet and shoot throughout the year will experience air densities that range from those typically found between 1500 feet below sea level to over 5000 feet above sea level -- a range of around 7000 feet. So simply changing the altitude of the place we stand does not even begin to tell the whole story on air density. Therefore, since altitude alone cannot be the whole story on air density, it cannot be the whole story on pattern variation.

Quote:
I used to use a sling psychrometer several times a day and night for most of 20 years. It determined our stay times in the main engineering spaces. Altitude wasn't much of a factor as it was hopefully always at sea level. If not there was a real problem LOL. Although we did strive for 29.9" of mercury inside the condensers.


This is irrelevant. As you know, psychrometry is the measurement of the water content in air -- humidity -- and its effects on things. Certainly you had figures of merit that your psychrometric readings had to stay between for certain reasons. It sounds from what you say, those reasons had to do with human endurance in those "main engineering spaces" (aboard a ship perhaps?), which might have been hot and humid. Psychrometric data is just wet bulb temp (water saturated air temp) and dry bulb temp (ambient air temp) from which you can calculate relative humidity, and know ambient temp. Psychrometry has nothing to do with air pressure. To calculate air density you need wet bulb, dry bulb and ambient air pressure (barometric pressure). Just my guess, but calculation of actual air density was probably irrelevant to the purpose of your checks on wet and dry bulb temps, and the range within which you were trying to stay.

I do agree with you that a 40 to 50 percent pellet count change is a lot and can occur, and no doubt merits some accounting for in choke selection for some shooting situations.
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Square Load
PostPosted: Fri Jan 10, 2020 10:18 pm  Reply with quote
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MSM2019 wrote:
So now I will ask.......with the exception of Wyochukar, who on this forum hunts at both 900' and 7,300' of altitude?

OK so how many of us have to even think about this?


I have hunted ruff grouse in WI at less than 900' , Blue grouse in Utah at almost 11,000' and a whole lot of places in between.

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fin2feather
PostPosted: Sat Jan 11, 2020 7:55 am  Reply with quote
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I think we've just hit the epitome of over-think Rolling Eyes

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Cold Iron
PostPosted: Mon Jan 13, 2020 1:30 pm  Reply with quote



Joined: 09 Mar 2016
Posts: 746
Location: Mn.

MaximumSmoke wrote:
Quote:
His Masters was in Statistics which is how he made his living, and that is really all a shotgun pattern is, statistics.


1) Statistics is not Physics (believe me I know, check my credentials, it's how I made my living)
2) We're not talking statistics when we are talking about air density effects on pellet flight, we are talking about a physical effect, not a statistical one -- to wit, the air-flow interference, pellet-to-pellet, in a shot cloud.

The only use of statistics in shotguns is to quantify the repeatability characteristics of shotgun patterns and ballistics, both internal and external. We do not use statistics to examine pattern spread, which is the subject of the article's premise.

Let's be clear on the subject. The article proposes air density is a significant factor in pattern spread, and covers experiments to show that. But instead of air density, altitude is posited to be the factor of influence in the article. However, air density, while obviously depending on altitude, is also highly dependent on temperature. Further to the demonstration of that fact, we in Minnesota, for example, who live at 900 feet and shoot throughout the year will experience air densities that range from those typically found between 1500 feet below sea level to over 5000 feet above sea level -- a range of around 7000 feet. So simply changing the altitude of the place we stand does not even begin to tell the whole story on air density. Therefore, since altitude alone cannot be the whole story on air density, it cannot be the whole story on pattern variation.

Quote:
I used to use a sling psychrometer several times a day and night for most of 20 years. It determined our stay times in the main engineering spaces. Altitude wasn't much of a factor as it was hopefully always at sea level. If not there was a real problem LOL. Although we did strive for 29.9" of mercury inside the condensers.


This is irrelevant. As you know, psychrometry is the measurement of the water content in air -- humidity -- and its effects on things. Certainly you had figures of merit that your psychrometric readings had to stay between for certain reasons. It sounds from what you say, those reasons had to do with human endurance in those "main engineering spaces" (aboard a ship perhaps?), which might have been hot and humid. Psychrometric data is just wet bulb temp (water saturated air temp) and dry bulb temp (ambient air temp) from which you can calculate relative humidity, and know ambient temp. Psychrometry has nothing to do with air pressure. To calculate air density you need wet bulb, dry bulb and ambient air pressure (barometric pressure). Just my guess, but calculation of actual air density was probably irrelevant to the purpose of your checks on wet and dry bulb temps, and the range within which you were trying to stay.

I do agree with you that a 40 to 50 percent pellet count change is a lot and can occur, and no doubt merits some accounting for in choke selection for some shooting situations.


You were the one that brought up the sling psychrometer Tony.

Altitude and air density ARE closely related. This is why airport runways at higher elevations are much longer. And why a baseball hit out of the park at the Twinkies home stadium will travel more than 30' farther, on average, at Coors Field in Denver. Less air density and drag at higher elevation. Which is the most likely causation for increased pattern density and central core thickening of shotgun patterns.

If there is another factor or factors that come into play what may it\they be? Not saying they don't exist.

fin2feather wrote:
I think we've just hit the epitome of over-think Rolling Eyes


A Mod choke shot at or above 5,000 ft. will pattern a couple times tighter than any Full choke made at or near sea level. But don't over think it.
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bobski
PostPosted: Tue Jan 14, 2020 6:55 am  Reply with quote



Joined: 18 Feb 2018
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Location: va, ct, mo

man, talk about splitting hairs.
so whats next? now we must factor in barometric pressure?
its not like we are all parachutists whos lives depend on an automatic opening devices that work of air pressure sensors.
geeesh.
(btw....been there)
god help people hunting who while out on a walk see rain coming and must change chokes.
our forefathers are to be admired. fixed chokes made things easy.

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fin2feather
PostPosted: Tue Jan 14, 2020 7:36 am  Reply with quote
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Cold Iron wrote:
A Mod choke shot at or above 5,000 ft. will pattern a couple times tighter than any Full choke made at or near sea level. But don't over think it.


Oh don't worry; I won't.

bobski wrote:
god help people hunting who while out on a walk see rain coming and must change chokes.


Laughing

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MaximumSmoke
PostPosted: Tue Jan 14, 2020 2:10 pm  Reply with quote
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Cold Iron -- I remind you, I said:
Quote:
However, air density, while obviously depending on altitude, is also highly dependent on temperature.


That is clear, but your constant denial that air temp is a major factor in air density is confounding. I gave a good example of the effect; I gave you a way to calculate it -- a way myself and all other aviators are trained to calculate air density and understand what affects it -- a method we use to estimate aircraft performance for safe flight. In the aviation community, as well as others depending on air density, this is a universally and fundamentally accepted method, and it clearly shows the strong effect of temperature.

I brought up psychrometry as an absurdity on how I should equip myself before any shooting event. Indeed using a psychrometer as part of a pre-shooting routine is absurd, and a splitting of hairs, just as bobski has stated. I have used psychrometric data to precisely calculate air density (particularly relative oxygen content) for the proper jetting of carburetors of roadracing motorcycles. Again, use of a psychrometer for good basic air density calculations is splitting hairs, though necessary for greater precision -- precision probably unnecessary to experiments on shotgun patterns, but so easy to get I don't know why an experimenter would ignore it. Anyway, you didn't get the joke. That's OK. I think you thought your response would somehow defend your thesis that temperature is not a considerable factor in air density, but it didn't. It was apparent you weren't using psychrometric data to calculate air density, only humidity for the sake of human endurance in a work environment. Don't get me wrong; I don't deny it was a good and necessary use of psychrometric data. Your response just had nothing to do with the subject of the discussion -- air density.

Barometric pressure? That would not necessarily be splitting a hair, but it's still not a factor everyone really needs to be prepared to examine before shooting. However, to evaluate a result assumed to be caused by air density, if one used just one parameter, barometric pressure would be a far, far better parameter than altitude. i.e. As long as one is making a rough calculation of air density, barometric pressure is a much better indicator of it than mere altitude.

Again, I do not deny air density has an effect on pattern spread; I never did. An article has been written that tries to quantify the effect, but it contains a defect. The article jumps to the assumption that altitude, for all intents and purposes, equates to air density, and it just isn't true. I have never denied altitude is a major factor in air density, either.

Any test of the influence of air density on pattern spread should take better account of air density, based not on altitude, but on barometric pressure and temperature, at the very least. It's so easy even an aviator can do it! Collection and use of humidity data would make air density calculation even more complete and credible, though humidity is a smaller effect. All this could be done easily (could have been done easily).
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Charles Hammack
PostPosted: Tue Jan 14, 2020 9:02 pm  Reply with quote
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Folks let's all go to the reservation , get up at 4 am drive 20-50 miles get out and start hunting .

20 miles later let's all get back in the truck drive back to Moo Dairy , put up birds in freezer , eat and get to bed by 11 pm .

Do this all over again for just 3 days.

End of third day let's all have this same discussion on the fourth day .

Be interesting to see what comes out 🤗🤗🤗🤗.

The folks all refer to this as bird hunting boot camp .

It's really interesting to see the second day what everyone takes and does
and what they don't take 😂.

Thanks everyone for telling about your vocation and experiences , listing equipment that I have to research to find out what it does.

Best regards , Nick
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double vision
PostPosted: Wed Jan 15, 2020 6:06 am  Reply with quote
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See bird-shoot bird!

That's about all my brain can handle.
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fin2feather
PostPosted: Wed Jan 15, 2020 7:46 am  Reply with quote
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Location: Kansas High Plains

Dave Erickson wrote:
See bird-shoot bird!

That's about all my brain can handle.


That pretty well sums it up.

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Pine Creek/Dave
PostPosted: Mon Feb 10, 2020 11:09 am  Reply with quote



Joined: 17 Mar 2017
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Location: Endless Mountains of Pa

F2F,

I agree, I have never been any where in the world hunting Grouse that the elevation had any real effect on my shells and gun, so that the Grouse did not fall when the gunning was done properly. The effect is usually on me and how I am unable to breath correctly. The mountains in AZ while hunting Mearns Quail definitely slow this old man down.

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L.C. Smith Man

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WyoChukar
PostPosted: Mon Feb 17, 2020 11:48 pm  Reply with quote



Joined: 16 Jul 2015
Posts: 2124
Location: Hudson,Wy

Air resistance is what opens a pattern. In the vacuum of space, a shot charge would essentially remain as a slug unless acted upon by other forces.

Environmental factors that increase air resistance: humidity, temperature (inversely:lower temp=more resistance), wind/ air velocity against projectile, and atmospheric pressure (forces more air molecules into a cubic foot of air-this is where elevation factors in).

Induced factors that increase air resistance: velocity and shot deformation. Bear in mind that a 20% increase in speed results in a much greater than 20% increase in resistance, especially with a round projectile.

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