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Sea level & Atmospheric Pressures vs. Accuracy


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I was watching some old Muscle Car drag racing videos yesterday on YouTube and

in part of the presentation, the Sea Level, Atmospheric Pressure, Temp, etc...... were listed

as part of the information data of the races.    This I can understand.

 

BUT.....

Does the Sea Level, Atmospheric Presssures, Temps, etc..... effect the Accuracy of our

firearms at SASS/CAS target distances?

AND..... can it adversely effect BP firearms within the ranges of SASS target distances?

 

I'm sure it makes a difference at greater distances, but I'm speaking only of SASS/CAS target distances.

Thanks!

 

.........WIdder

 

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Oh so that's why I'm missing!!!!:lol:

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5 minutes ago, The Rainmaker, SASS #11631 said:

I would think only temp and humidity would affect us and only at extremes.

Altitude/atmospheric pressure... ehhh, I doubt it. Not for CAS distances.

Oh c'mon this is a great excuse for misses!!:lol:

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What about the tide level?  If the moon has enough gravitational pull to move the ocean, then it certainly can move a little bullet.  This may explain my recent miss at EOT.

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20 minutes ago, Badlands Bob #61228 said:

What about the tide level?  If the moon has enough gravitational pull to move the ocean, then it certainly can move a little bullet.  This may explain my recent miss at EOT.

Of course the tide effect might have been pulling on the liquid in your dominant eye causing you to, once again, miss with your left pistol.  Come to think of it you do have an affinity for left hand tidal misses, especially on Saturdays.  You might want to look into that Evil Bob.:lol:

 

Kajun

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I've only seen low temperatures, high and low humidity and heavy (or lack of) wind directly affect cowboy shooting ballistics and reliability.

 

Low temperatures - because some powders are weaker performers in cold temperatures, and we typically shoot some of the lightest loads in the shooting world, our shooting can be significantly affected by temperatures of freezing or below.   Of course, testing "frozen" ammo. can be easily done now, since everyone has their own Yeti.  And, remember, there is a rules-based lower velocity limit and a lower power factor limit for Cowboy, and a more restrictive limit for Wild Bunch .  Cold mornings can certainly make it possible to be in violation of velocity/power requirements.

 

Heavy wind - mostly by blowing up dust to obscure targets and fill guns with grit, to point of not being operational.   High humidity and no wind - these atmospheric conditions allow black powder and substitutes smoke to collect and obscure targets.   (And SASS rules warn of that possibility)   Low humidity and high air temperatures make BP fouling harder and produce more barrel deposits, and might decrease accuracy enough to be noticeable at side match ranges.

 

Now, there can be lots of weather effects on the shooter's ability to navigate the stage.   But I figure you already have those well under foot and in hand.

 

And as for affecting accuracy?  In Cowboy shooting?  How the heck can you tell, when there's not even "minute of steel accuracy" under the best of conditions?  :lol:

 

good luck, GJ

 

 

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The only thing that may affect anything at CAS distances is temperature. Picture your ammo baking in the sun in your cart, the rounds are so hot they burn your fingers and thus, raise pressures. On top of this, it's so bloody hot, you can't seem to remember the stages. Next imagine your ammo at a cold weather shoot. Your fingers are a bit stiff pulling your shotgun shells and the ignition on your cartridges is a bit (or a lot) inconsistent due to the low temperatures.

 

Thin dry air vs. heavy, humid air won't make a speck of difference at CAS distances.

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SASS distances have been answered. I did see cold temps drastically effect some smokeless powders.

I experienced first hand the effects of altitude and atmosphere playing golf. Played in So. Calif. Moved to Reno, NV 800' to 4,700 feet elevation. For the same distance you dropped one club for Reno's altitude. an 8 iron instead of a 7 iron as an example.

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Temperature will affect pressures and velocities, especially with smokeless powders.  Some smokeless powders can be low-temp sensitive, especially if you are loading at the minimum recommended for a particular powder, at room temperature. (Sorry, I don't know which ones.  Check with Hodgdon's.)  Conversely, if you are normally loading near the maximum listed load at room temperature and go shoot at 100+ degrees F., you may exceed the SASS maximum for velocity.  Pressures may go up to a dangerous level.  Worse then just the Outside Air Temperature (OAT) is if you leave your ammo in the unairconditioned car, or in the sun in a container such as a .50 cal. ammo "can".  

 

Altitude won't change the accuracy as much as it will change longrange ballistics.  Sighting a hunting rifle in at sea level and then going hunting in Colorado will not only flatten the trajectory, but can change the bedding of your rifle. (Think what pitchers face when pitching at Tampa Bay versus Coors Field in Denver!)  For SASS ranges, it won't make a difference.

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Quote

 

Does the Sea Level, Atmospheric Presssures, Temps, etc..... effect the Accuracy of our

firearms at SASS/CAS target distances?

AND..... can it adversely effect BP firearms within the ranges of SASS target distances?

 

I'm sure it makes a difference at greater distances, but I'm speaking only of SASS/CAS target distances.

 

ZERO IMPACT on accuracy

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4 hours ago, Widder, SASS #59054 said:

I was watching some old Muscle Car drag racing videos yesterday on YouTube and

in part of the presentation, the Sea Level, Atmospheric Pressure, Temp, etc...... were listed

as part of the information data of the races.    This I can understand.

 

BUT.....

Does the Sea Level, Atmospheric Presssures, Temps, etc..... effect the Accuracy of our

firearms at SASS/CAS target distances?

AND..... can it adversely effect BP firearms within the ranges of SASS target distances?

 

I'm sure it makes a difference at greater distances, but I'm speaking only of SASS/CAS target distances.

Thanks!

 

.........WIdder

 

 

Depends upon whether you're shooting uphill or downhill.;)

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4 hours ago, Widder, SASS #59054 said:

I was watching some old Muscle Car drag racing videos yesterday on YouTube and

in part of the presentation, the Sea Level, Atmospheric Pressure, Temp, etc...... were listed

as part of the information data of the races.    This I can understand.

 

BUT.....

Does the Sea Level, Atmospheric Presssures, Temps, etc..... effect the Accuracy of our

firearms at SASS/CAS target distances?

AND..... can it adversely effect BP firearms within the ranges of SASS target distances?

 

I'm sure it makes a difference at greater distances, but I'm speaking only of SASS/CAS target distances.

Thanks!

 

.........WIdder

 

Depends... supercharged or fuel injected? Both?

Nitro or Sunoco Blue?

What's the timing set at?

Open headers or closed exhaust?

Facts man, we need the facts! :D

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3 hours ago, Garrison Joe, SASS #60708 said:

I've only seen low temperatures, high and low humidity and heavy (or lack of) wind directly affect cowboy shooting ballistics and reliability.

 

Low temperatures - because some powders are weaker performers in cold temperatures, and we typically shoot some of the lightest loads in the shooting world, our shooting can be significantly affected by temperatures of freezing or below.   Of course, testing "frozen" ammo. can be easily done now, since everyone has their own Yeti.  And, remember, there is a rules-based lower velocity limit and a lower power factor limit for Cowboy, and a more restrictive limit for Wild Bunch .  Cold mornings can certainly make it possible to be in violation of velocity/power requirements.

 

Heavy wind - mostly by blowing up dust to obscure targets and fill guns with grit, to point of not being operational.   High humidity and no wind - these atmospheric conditions allow black powder and substitutes smoke to collect and obscure targets.   (And SASS rules warn of that possibility)   Low humidity and high air temperatures make BP fouling harder and produce more barrel deposits, and might decrease accuracy enough to be noticeable at side match ranges.

 

Now, there can be lots of weather effects on the shooter's ability to navigate the stage.   But I figure you already have those well under foot and in hand.

 

And as for affecting accuracy?  In Cowboy shooting?  How the heck can you tell, when there's not even "minute of steel accuracy" under the best of conditions?  :lol:

 

good luck, GJ

 

 

One Gent at EOT in NM said he put his pistol/rifle ammo in his rv freezer...

He felt the high altitude, dryness and heat was affecting his rounds.

Said after using the 'frozen' ammo...all worked without a hitch.

Soooooo....answer is still up for grabs.

Edited by Singin' Sue 71615
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Think Karma is SASS shooters worst enemy other than heat and humidity      GW

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Where is Noz??  He is a retired Army Field Artillery Officer.

 

When you are trying to drop an explosive shell in someone’s hip pocket 20 miles away, EVERYTHING matters.

 

At SASS target distances, you are the only thing that matters.

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6 hours ago, Singin' Sue 71615 said:

Said after using the 'frozen' ammo...all worked without a hitch.

 

Some powders are great when cold.  Many are not.  Clays is one that is VERY well known to be weaker in cold weather.

 

On the other hand, a few powers are stronger when cold.  WST is well known for being exactly that - higher chamber pressures when cold and lower pressures when hot.  Which is one more reason it's my favorite pistol/shotgun powder.  It stays so consistent over temps from 20 F to 140 F.

 

good luck, GJ

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15 minutes ago, Garrison Joe, SASS #60708 said:

 

Some powders are great when cold.  Many are not.  Clays is one that is VERY well known to be weaker in cold weather.

 

On the other hand, a few powers are stronger when cold.  WST is well known for being exactly that - higher chamber pressures when cold and lower pressures when hot.  Which is one more reason it's my favorite pistol/shotgun powder.  It stays so consistent over temps from 20 F to 140 F.

 

good luck, GJ

I wish I could remember who it was that was putting his rounds in the freezer.... maybe they will speak up!:rolleyes:

You know my knowledge is "that it goes bang"!!!!

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Altitude has a big effect on internal combustion engines. As the air pressure drops cylinder filling becomes less.  At 11,000 ft you lose about 50% of sea level hp.  
 

I believe since powder contains its own oxidizer, altitude has little to no effect on burn rate.  Air resistance is less, so shot shells should pattern a bit tighter.  Probably no real effect on bullets at sass ranges. 
 

it also effect the boiling point, so cooking takes longer.  

Edited by Still hand Bill
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34 minutes ago, Still hand Bill said:

Air resistance is less, .......    Probably no real effect on bullets.  

That would be a wrong assumption.   Air density (and even temperature) has a major effect on velocity decay and trajectory.   Due to drag on the bullet.   Lots more drag at sea level than at 10,000 feet.   But, not to worry when shooting at most cowboy distances.    Snipers, however, have to pay real attention.

 

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12 hours ago, J-BAR #18287 said:

Where is Noz??  He is a retired Army Field Artillery Officer.

 

When you are trying to drop an explosive shell in someone’s hip pocket 20 miles away, EVERYTHING matters.

 

At SASS target distances, you are the only thing that matters.

When we were tasked with first round unregistered accuracy we would constantly refer to weather radio for updates.  Even the rotation of the earth for the time the 200 lb. round was in the air was significant.  All of the calculations were done with pencil and paper instead of computers.  I will admit we did use a slide rule for some of the more complex situations.

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On 7/19/2021 at 5:25 AM, Widder, SASS #59054 said:

I was watching some old Muscle Car drag racing videos yesterday on YouTube and

in part of the presentation, the Sea Level, Atmospheric Pressure, Temp, etc...... were listed

as part of the information data of the races.    This I can understand.

 

BUT.....

Does the Sea Level, Atmospheric Presssures, Temps, etc..... effect the Accuracy of our

firearms at SASS/CAS target distances?

AND..... can it adversely effect BP firearms within the ranges of SASS target distances?

 

I'm sure it makes a difference at greater distances, but I'm speaking only of SASS/CAS target distances.

Thanks!

 

.........WIdder

 

Hatcher's Notebook discussed that.  The effects are negligible in hand-held firearms. 

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  Actually atmospheric pressure  tremendously affects accuracy at sass distances; although individual effects will vary. After what started as a minor niggle and grew to tremendous proportions I performed an intense multi-year experiment into hits vs misses. Without expounding on all of the various trials and tribulations I went through, I will give my finding and thus resulting theory.

 

It ain't mattered where I was or what I was a doing. I ain't never had no miss what didn't have some atmospheric pressure involved it somewhere. That there's the common denominator!

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