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Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

 
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  #1  
Old 10-11-2009, 07:24 PM
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Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

Quote:
It’s a well established scientific fact that air temperature influences muzzle velocity, and under some field conditions that variation can be quite significant, in particular for taking a long range shot.

Recent tests showed a rate of change of about 2.5 to 4.0 feet/sec per 1°C (1.8°F) depending on how sensitive the load’s powder is to air temperature.

Just to give a basic perspective, a muzzle velocity variation of +/- 30 feet/sec can introduce a change in the trajectory’s path of about 1.0 MOA at 1000 yards, (+/- 0.5 MOA) and of course, there is uncertainty that must be accounted for.
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Old 10-13-2009, 10:52 AM
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Re: Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

Now that I have rifles that can be shot consistently and a accurately that kind of detail gives me the warm fuzzies. Used to give me the vapors.......

Great article.
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Old 10-20-2009, 09:09 PM
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Re: Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

Excellent reading!!!
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Our Lord Jesus said that as it was in the days of Noah and
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to this generation and we once more are rejecting it as was prophesied!!!

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Old 10-21-2009, 06:27 AM
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Re: Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

This seems statistic hoo humery masking validation, conclusion, and basis..
Where is contrast taken into account with a scientific method?
Barrel type-vs-rifling method-vs-Barrel steel temp -vs- powder type-vs- powder temp -vs- air density-vs-rate of fire???

Connecting a few dots just doesn't always hold real meaning.
If alot of math is needed(and I'm sure it is), then it would surely include 'Design of Experiments'

Last edited by Mikecr; 10-21-2009 at 06:48 AM.
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Old 10-21-2009, 09:42 AM
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Re: Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

Quote:
Originally Posted by Mikecr View Post
This seems statistic hoo humery masking validation, conclusion, and basis..
Where is contrast taken into account with a scientific method?
Barrel type-vs-rifling method-vs-Barrel steel temp -vs- powder type-vs- powder temp -vs- air density-vs-rate of fire???

Connecting a few dots just doesn't always hold real meaning.
If alot of math is needed(and I'm sure it is), then it would surely include 'Design of Experiments'
Seems to me that a second reading is worth the time...

1- Math content was excluded on purpose to make the piece more readable.

2- It's pretty clear and obvious that MV contains in itself all variations due to an specific load/firearm, as explained in the article.

3- This is not, by any means, an article on how a barrel-type or powder affects MV. In fact, that's not required at all for the stated purpose.

4- The piece's objective is quite clear as explained in the initial paragraph.

5- What is called for is for a technique, based on sound statistics, to calculate interpolation and extrapolation under limited datasets of MV/Air Temp pairs.

6- The article clearly explains that the independent variable, Air Temperature, limits the general idea, to what's important, a "first shot from a cold-bore". So no need at all for "rate of fire"...

7- What you mean by "contrast"...? again, the article explains how different Regression methods can be employed and the differences between them. That's the whole idea, as clearly stated.

8- I never said nothing about "connecting dots" to perform other analyses rather than the exposed central idea...which is about different Regression methods.

9- A "Delta Spline", for anyone who is interested in, will take about six pages to derive and explain, which is way beyond the scope of this forum.

10- On a sidenote, this method was developed to comply with a military contract for a sniper ballistics package, now fielded.

11- On the other hand, LoadBase 3.0 (Desktop and Mobile) provides all the tools that are required to make meaningul decisions and calculations, based upon an observed dataset (Field Data of MV/Air Temp readings)
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regards, Gus

LoadBase© Desktop & Mobile editions - the ballistics/reloading software solution
http://www.patagoniaballistics.com
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  #6  
Old 10-21-2009, 05:01 PM
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Re: Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

So re-reading the first section of the article, should I take this solely as 'use of statistics to draw conclusions with limited data'?
Perhaps if it were titled as such..

Because in my view, the article itself 'proved' nothing.
It went unqualified with regard to the title: "Air Temperature Effects On Muzzle Velocity"...

For example, in the opening statement: "It’s a well established scientific fact that air temperature influences muzzle velocity". Well, is this true? Is it something you've qualified, taken with contrast, validated, proven and defined? Seems a foregone conclusion otherwise.
If I setup a chrono and rest at a bench, while it's 0degF out, then quickly pull a gun & ammo out of truck, set it down and fire across the chrono, will velocity be different now than it was 6mos ago while it was 90degF out?
And what if it were both a 30cal AND a 22cal in such a scenario?

I suggest a prediction might not be as simple as it seems.
Does the heater work in my truck? Does it even matter?
What if I left a 30cal gun/ammo AND a 22cal gun/ammo on the bench at 0degF for one additional hour and fired them? And 3hrs?
What if I left the guns out, but kept the ammo in my pocket between shots?
Or if only the ammo was exposed?
This is an example of CONTRAST.
It's very important because despite statistic delusion, only the truth passes ALL tests. So you cannot know the truth until you've challenged it from many many angles and validated that it still does not fail.
If you define ONE validated truth with statistics, you should take care to qualify that as such.

It just seems a stretch to understand what we're to take away from your article, thats all.
Was it a plug for Patagonia?
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Old 10-21-2009, 06:14 PM
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Re: Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

Mikecr,

I'll let Gus respond, but I believe the intent of the article was to describe how, once the preferred load has been developed for a rifle, a person can chronograph MV at a few differing ambient air temps (I believe a minimum of 4 temps & this assumes cartridge and rifle are also at ambient air temperature), and then use this statistical approach to model MV at other temperatures reasonably accurately, based solely on the original set of chronographed MVs at the known temperatures.

In practice, having collected the MV data for your pet cartridge/rifle combination, and having the ouput from the statistical modeling merged into the Patagonia ballistic software - then when one collects the atmospheric conditions in preparation to determine corrective dope for the long range shot, the ballistic software will modify the MV to match the actual air temperature, resulting in corrective dope that will most accurately match the catridge's MV in those ambient air temperatures.

If you're going to keep your ammo in your pocket at body temperature and load and shoot before the gun's chamber cools or heats up the cartridge, then it wouldn't be appropriate to rely on ambient air temperature to model MV. But, if you're ammo and rifle are allowed to reach ambient air temperature, then for at least the first shot, the use of this statistically modeled MV value in the ballistics engine would yield a close to correct MV and dope.

I happen to own and use the Patagonia software so I could follow the intent and application of article. It was not meant to cover all possible affecting aspects of air temperature on MVs. Chrono MV at a minimum of four different Air Temps, allowing rifle and cartridge to reach ambient air temperature prior to shooting over the chronograph. Enter the MVs and matching air temps values. Premise is that MV will then be statistically modeled to closely match actual MV at the current conditions ambient air temperature. The modeled MV value then gets cranked through the ballistics engine to provide the best corrective dope possible for the shooter's ambient air temperature.

Last edited by phorwath; 10-21-2009 at 06:49 PM.
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