Discussion in 'Technical Articles - Discussion' started by ADMIN, Oct 11, 2009.

# Air Temperature Effects On Muzzle Velocity

1. ### ADMINAdministrator

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This is a thread for discussion of the article, Air Temperature Effects On Muzzle Velocity, By Gustavo F. Ruiz. Here you can ask questions or make comments about the article.

2. ### royinidahoWriters Guild

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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.

3. ### EagletWell-Known Member

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Excellent reading!!!

4. ### MikecrWell-Known Member

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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: Oct 21, 2009
5. ### GustavoWriters Guild

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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)

6. ### MikecrWell-Known Member

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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?

7. ### phorwathWell-Known Member

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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: Oct 21, 2009
8. ### GustavoWriters Guild

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One more time, this article is all about Data Regression techniques, using the data most likely at hand, which is Air Temperature, used to derive MV as a result.

Any other issues, like the ones posted are not discussed, simply because that's not the central subject of the piece. That's the terrain of Interior Ballistics.

What the article explains and shows (and proves to some limited extent) is that a "Delta Spline" is the best possible method to infer interpolated/extrapolated values.

Of course, I'm not stating that other factors do not matter. Far from that.

And yes, to answer your question, it's a well established fact that Air Temperature affects MV...for the conditions given in the article.

The military (and some other independent labs) have a good number of tests (which are limited to certain border conditions) showing the correlation as stated.

In short, if you have measured MV/Air Temp pairs (KDPs) you need a technique to extract meaningful predicitions for values outside the tested range (a limited dataset).

If that's the case, well, this article exposes which techniques are best and why, in terms as simple as possible.

Now, you being the end user, is up to you to decide under what conditions the KDPs were obtained, and to repeat that same criteria when using the software.

The method(s) cannot infer nothing about the conditions, just provides the best possible math to derive a best "curve fit" to the sample data.

On the other hand, LoadBase 3.0 gives the end-user the tools to study and qualify the sample data, even to highlight "suspect" KDPs.

Statistics is a very powerful tool, but cannot compensate for erroneous criteria or bad judgement. Magical it's not.

9. ### EagletWell-Known Member

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Mikecr,

I'm also a user of LoadBase 3.0 and I intelligently understand what Gus is clearly bringing across. Not trying to bring across, but very successfully exposed.

I don't understand your position, but then again there's a bunch of things I don't understand.

Perhaps if you read it again with the right attitude would help.

Last edited: Oct 21, 2009
10. ### yobuckWell-Known Member

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there is no doubt temperature affects trajectory,and
some powders are affected more than others.
many of us leave ammo in vehicles on our hunting trips where overnight temperatures can take affect.
there are other things like wind that can affect it also.
obviously there are some who can really get into the technical aspect of all this.

for the average hunter like me for example, who dosent understand fully, or even care to, what does he do?
i think the solution is simple. if you want to shoot at long distance, always use a spotter.
who cares why you missed, you still missed. make the corrections reccomended by your spotter and shoot again.

11. ### phorwathWell-Known Member

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To each his own. Some of us enjoy the challenge of doing everything possible to try to place the first shot on the button. I don't claim to always do that, but I find it satisfying to understand the fundamentals and then getting it right the first time around - when it all comes together for me.

My purpose isn't to criticize. Just to point out that "different strokes for different folks" is always in-play.

Another thought I have is I often hunt by myself. I enjoy that challenge also. So the ballistic software fills an important role for me.

Either way - good hunting to ya. Hunting is an invigorating hobby.

12. ### docv_73Member

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Use your imagination... picture me... scratching my head...

?????????

When I was in the military, the standard was adjust 1 MOA for every 20F.

The first few sentences seemed to confirm, or at least assimilate that approach.

Then I looked at this article titled "...airtemperature..." but what I think I read, was a thesis for a doctorate about data collection.

I usually consider myself a very intelligent person but that was a lot to take in....

Is there a simple conclusion to that?

Is the standard that was taught to military snipers 20 years ago correct or not?

Last edited: Jun 18, 2010
13. ### yobuckWell-Known Member

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for a hunter there is a simple conclusion, YOU MISSED. add some more elevation and shoot again.

14. ### MikecrWell-Known Member

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No yobuck, if YOU MISSED, you mgiht as well pack up your stuff & go to the house.
Then consider why it is you can't hit what you're shooting at, and what your capabilities truly are, -before venturing into further hunting...

Eventually you'll seperate yourself as a competent hunter, from menace.