Air Temperature Effects On Muzzle Velocity By Gustavo F. Ruiz

[CRaTxn]

Mikecr I find your comments invigorating and intelligent but how can you say "But the truth is temperatures have nothing at all to do with altitude" when we incorporate the standard adiabatic lapse rate into our climb and descent performance engineering profiles for aviation ? Does the 2*c/1m' not mean there is a relationship to you ? You and and I are kind of like boys on the playground fighting over some meaningless something when in truth we share a love of hunting and I hope can become at least acquaintances for surely you demonstrate an advanced skill level here. Please let this be an academic not emotional exchange.

 

[Pdvdh]

I think the correlation of altitude, temperature, and pressure is relative in the present sense, meaning if you set your instrument adjustment to current conditions, the relationship is likely to be present the majority of the time. But I've climbed up into the sheep mountains in 40F weather, and I've been present at the same altitudes when the temperature was 80F. Unless you're going to select and install new turrets based on current weather conditions, the same way you set a planes instruments to the present conditions, I don't see where the rule of thumb would be helpful throughout the duration of a hunt, under changing weather patterns. At least not where I've hunted. Maybe I'm missing something here, but weather is transient - ever changing - and my hunts often last long enough to encounter differing weather patterns and their resultant differing temperatures. Let alone the daily temperature swings from morning to mid-afternoon to evening.

Seems much more straightforward to simply obtain the current temperature and station pressure at the time and location of the pending shot, and then determine and apply the appropriate dope based on those current environmental conditions.

 

[Mikecr]

how can you say "But the truth is temperatures have nothing at all to do with altitude" when we incorporate the standard adiabatic lapse rate into our climb and descent performance engineering profiles for aviation ?

Aviation and ballistics share nothing in common.
With successful LR shooting we don't 'incorporate' any standard assumptions. We measure ACTUAL conditions for what they are, and adjust as appropriate. We're are not estimating altitude, and could care less about it really.
Our concern is actual local air density.
phorwath explained it well.

 

[HarryN]

Thank you for the excellent article, and the comments.

I am still a beginner / student in the long range concepts, but I am familiar in general with temperature effects on various hardware and chemical processes.

It occurred to me that if barrel temperature, bullet, and powder temperature are such major factors in trajectory planning, then one possible method to reduce this is to heat the barrel to a relatively narrow constant temperature, or at least to a "minimum" temperature.

I know that sounds easier than it is, but it is possible, at least under some conditions.

 

[DocUSMCRetired]

To calm down some of the arguing with scientific fact. I did read the date on how long ago the last post was, but I wanted to provide some scientific input.

Fact an increase in temp causes the nitro cellulose based powder to burn at a faster rate. This causes a change in impact that is 4 times what simply air temp change alone causes. Of course not all powders are effected the same. This change in powder temperature will change your muzzle velocity, some more than others as some powders are more stable. Changing muzzle velocity will always change your ballistic curve.

How to over come this is easy. Our software allows you to calibrate for this change in muzzle velocity by inputting the different muzzle velocities you get at different temperatures, then it builds a solution for you based on this. Effectively helping to calibrate your ballistic curve.

Applied Ballistics Support Staff
[email protected]

 

[Mikecr]

Yes, and this would correlate to an article called:
'Potential Powder Temperature Effects On Muzzle Velocity'
Written by BuyOurSoftware, [email protected]

You could bring us some 'scientific input' there.

 

[bootsking]

From a strict statistical perspective this appears to be a classical application of "over-fitting", meaning there needs to be some reason to use a more complex model (eg spline, etc) to simply make the curve go through all of the data points. What is the technical reason that suggests this extreme complex behavior? In this case the most fundamental rationale is to first determine the velocity variance at a given temperature (we know it is not constant, as evidenced by the usual characterization of the standard deviation), and compare resulting error of the simplest regression to judge whether a more complex model is needed. In other words statistical analysis supports the KISS principle!