Humidity, temperature and powder

[Vern]

Ok here it goes. Read the whole post before you react.
I am just trying to gather info on what is known and pose a scenario to ask questions.
After all the years of reading and shooting it is usually stated that temperature and humidity affect the powder which affects the tune (if we can call it that for the sake of argument).
For general considerations we could say we are discussing the 6ppc to prevent any,,,,, well now that depends options.
If we preloaded at home and went to the range to find our tune and we find that xx.y charge of z brand of powder at a set depth gave us what we considered a perfect tune.
The load being assembled at 75 degrees and 30% humidity climate controlled. Shot on an 80 degree day where the temp,humidity and wind were constant during the session. (yea I know dream on)

1. If we again loaded the same load under the same climate controlled conditions and shot it under the same conditions at the range should we expect the same results?
2. If we used the same loads made under climate controlled conditions and shot it on a day that was 95 degrees and 60% humidity with the same wind as the previous session would we get the same result?

In either of these scenarios the external humidity can not affect the powder or powder ignition/burn already in the cases. Can it?
What effect will the external temperature and humidity have on loads that were loaded under climate controlled conditions.

 

[goodgrouper]

Ok here it goes. Read the whole post before you react.
I am just trying to gather info on what is known and pose a scenario to ask questions.
After all the years of reading and shooting it is usually stated that temperature and humidity affect the powder which affects the tune (if we can call it that for the sake of argument).
For general considerations we could say we are discussing the 6ppc to prevent any,,,,, well now that depends options.
If we preloaded at home and went to the range to find our tune and we find that xx.y charge of z brand of powder at a set depth gave us what we considered a perfect tune.
The load being assembled at 75 degrees and 30% humidity climate controlled. Shot on an 80 degree day where the temp,humidity and wind were constant during the session. (yea I know dream on)

1. If we again loaded the same load under the same climate controlled conditions and shot it under the same conditions at the range should we expect the same results?
2. If we used the same loads made under climate controlled conditions and shot it on a day that was 95 degrees and 60% humidity with the same wind as the previous session would we get the same result?

In either of these scenarios the external humidity can not affect the powder or powder ignition/burn already in the cases. Can it?
What effect will the external temperature and humidity have on loads that were loaded under climate controlled conditions.

Vern,

Answer to question 1: Yes. But, Murphy has a way of showing up at the gun range. I think we can expect the same results but we might not actually get them.

Answer to question 2: Very unlikely. That's enough of an environment change that it would show up in the tune.

As to your other questions, all I can tell you is this: I have thrown charges from a Harrells inside a motorcycle trailer that had propane running (very humid) and rain/snow falling outside (humid) and condensation from the hot/cold temp difference (humid) to the point where water beads were forming on everything. Dies, wet. Brass, wet. Press wet. Basically anything that was metal was wet. I took those loads and fired them over a chronograph and got x velocity and y accuracy. I then weighed what my thrower was throwing and it was z. Loaded up a dozen or so more rounds that day and saved them for later. Next time out, it was 70 degrees and 35% humidity. Fired them over the chrono again and they were within 10 fps of x velocity and pretty close to the same y accuracy. There was however, a slight change in POI at 100 yards. Then I weighed the same setting on my Harrells and it was exactly z again.
Since then, I have tuned for matches paying attention to nothing but temps and group size.
Now, I've listened to Jack Neary's sessions and talked to many other well respected shooters and they will tell you that humidity makes our throwers throw "heavier". Some even have said that humidity in the barrel makes the bullet "push" against "denser" air. Well, I don't doubt these guys. But I just haven't been able to prove what they've told me in my own experiments. That is why I love chronographs. They tend to shoot holes (pun intended) in lot's of folk's "facts" or "theories".
That being said, most of these folks who swear by (and at) humidity live in different parts of the country where humidity is usually higher. They also live at lower elevations. Other than Phoenix, all the matches I attend are 4000' or higher and a 40% humidity day is very wet for us. But, like in my example, it's hard to get wetter than water beads on everything!
On a related note, everybody east of the Mississippi complains that N133 won't work when humidity drops below 50%. Well, we use N133 out here most of the time too and we don't usually get UP TO 50% humidity. I've not found N133 to be anything like folks elsewhere describe it. So maybe some aspects of interior ballistics are different depending on where you're shooting?

 

[mks]

Humid air is less dense than dry air because H2O vapor is lighter than N2, which is the primary component of air. Seems backwards, but it's true.

 

[Vern]

GG
Thats why I posed the question with loads being created inside under basically ideal conditions.
Because of the ideas or facts (whichever) of powder being different when left and used under different temp/humidity conditions.
If the loads are created under the same exact conditions and the powder is essentially sealed inside the case then the outside humidity can not have an effect on the burning of the powder.
It would be left more to the temperature the powder is when its fired but not when its thrown.
The other would be related to the humidity that the bullet travels through.
I notice that your observation was that the velocity didnt change much.
The heat and humidity upon firing would account for the diff POI but what I am really wondering is if there was any affect on the tune (accuracy/grouping/agg) of the gun/loads.

More simplified....
Sometimes we have a never ending circle
We load at the range because we find that temp and humidity change the way our powder reacts to the elements before we throw it....so we change our load through out the day because of this effect on our powder as it sits at the range
WELL if we were not throwing it at the range.....the temp and humidity coundnt have that effect only on the bullet or the external temp affecting the burning.
HOW DOES TUNE CHANGE when eliminating the humidity and temp element powder is subjected to before it is put into the case.

Am I making any sense? Or am I just stirring up a bunch of mud?

We dont preload because the element can affect the powder while at the range.... but then if we preload how can the elements affect the powder.
Some say they take tubes with powder preweighed but then things can change.. but then the powder is there in the elements until it is sealed in the case at the range.

 

[alinwa]

Ok here it goes. Read the whole post before you react.
I am just trying to gather info on what is known and pose a scenario to ask questions.
After all the years of reading and shooting it is usually stated that temperature and humidity affect the powder which affects the tune (if we can call it that for the sake of argument).
For general considerations we could say we are discussing the 6ppc to prevent any,,,,, well now that depends options.
If we preloaded at home and went to the range to find our tune and we find that xx.y charge of z brand of powder at a set depth gave us what we considered a perfect tune.
The load being assembled at 75 degrees and 30% humidity climate controlled. Shot on an 80 degree day where the temp,humidity and wind were constant during the session. (yea I know dream on)

1. If we again loaded the same load under the same climate controlled conditions and shot it under the same conditions at the range should we expect the same results?
2. If we used the same loads made under climate controlled conditions and shot it on a day that was 95 degrees and 60% humidity with the same wind as the previous session would we get the same result?

In either of these scenarios the external humidity can not affect the powder or powder ignition/burn already in the cases. Can it?
What effect will the external temperature and humidity have on loads that were loaded under climate controlled conditions.

IMO if you preload the only requirement is that you should have a way to keep the temperature of the loaded ammunition fairly consistent. Like a cooler, and a thermometer if temps go really wonky.


Perhaps you will get some answers from people other than myself who've actually done the preloading thing. There are at least three competitors that come to mind who've been successful with it. One who occasionally posts here is a HOF shooter and he preloads to a specific velocity, loading at home to achieve this velocity. He states that he's had loads vary by as much as 1.5gr to get to the target velocity but that the loads perform well at matches. The question will be whether or not a day-to-day match shooter will want to open this can of worms on the 'net.

When I started shooting some 600yd matches 3-4 yrs ago I worried about the preloading aspect but I followed this advice, working up my loads to be velocity specific.

The one time I ran into trouble was a day that I got sloppy with my ammunition. I left the box out between relays, the day warmed up and the pressure went up.

IMO, if you tuned/loaded the rounds at 70 degrees, keep them at 70 degrees at the match and they'll shoot and maintain tune, rain-or-shine, thru anything. IMO external conditions DO NOT affect the tune.

This is most certainly an opinion. I hope some a' you'se go try it and report back.

al

 

[caroby]

HOW DOES TUNE CHANGE when eliminating the humidity and temp element powder is subjected to before it is put into the case.

Because most of the tune "reaction" is AFTERWORDS... I.E. Ignition through bullet impact on paper >in the condition of the moment<......... The effect on tune is mostly NOT due to loading condition BUT due to firing condition... Mostly...

Sometimes sutle sometimes NOT... I mostly agree with Grouper that Temp has more effect than Humidity... But...
Another issue is Altitude.......... Air density fellers..! >>>>

>>>

Humid air is less dense than dry air because H2O vapor is lighter than N2, which is the primary component of air. Seems backwards, but it's true

. <<<<

Yes Sir..

Then there are the range effects on the wind that the flags can't begin to show that make one QUESTION there "perfect" tune........

cale

 

[Boyd Allen]

Al,
To reinforce the "tune is velocity specific" idea, I can report that recently, I tuned up a benchrest rifle with very satisfying results, and being a curious sort, the next trip to the range (similar ambient conditions) I chronographed that load, then I proceeded to work up loads with a couple of different powders by changing the volume of the load till I hit the same velocity. The results were virtually identical to the first workup. It was a much faster route to finding a load with a different powder. Many times I read reports where someone has "tested" different primers or powders in a rifle. None that I can remember held velocity constant to a value established as shooting well in the test rifle, with one particular bullet and seating depth. I think that this points to the need to do one's own testing.

 

[Vern]

If tune is velocity specific (I am not arguing the point), how does bullet jam come into play?
Or barrel vibration?

 

[Boyd Allen]

I was using the same bullet, and seating depth. I have seen bullet jump (in a well built hunting rifle) tune similar to powder, going in and out of tune as the jump was increased. Some time, I plan on doing a little chronograph work to investigate what is taking place. It would be interesting to work up two loads that have the same velocity, with the same bullet, but had widely differing seating depths. When I wrote of tune being velocity specific, a thought that I got from Jim Borden, I assumed that he meant with the same bullet, barrel and seating depth, and that is the way that I did my multiple powder tune-up.

 

[goodgrouper]

Humid air is less dense than dry air because H2O vapor is lighter than N2, which is the primary component of air. Seems backwards, but it's true.

I remember the first time I said that very thing on this site...........thought they were going to send the dogs after me!

 

[goodgrouper]

Vern,

I related that story to show that neither humidity nor dry conditions made any difference on how much powder my thrower threw. Neither did it make any difference on how fast the ammo went.

So, I don't believe humidity affects the round you loaded at home or at the range as far as internal ballistics go. As I see it, temperature is the main driving force that raises or lowers pressures, so if you load at home, it makes sense to load for a wide node window and try to keep the ammo at the same temp from die to chamber.

If I were to load at home for short range competition, I'd be using a tuner to get peak accuracy as the temp changed the time my bullet spent in the barrel and thereby changing the point where the bullet was released in the oscillation.

 

[Vern]

Thank to all for the insight.