answer me this

goodgrouper

goodgrouper

tryingtobeabettergrouper
Been looking through some old Precision Shooting magazines lately and came across an article about loads going in and out of tune with humidity. The author said that he had a load that he would "pre-load" at home and it would shoot fantastic until the humidity became too high.

Well, being a ballistic nut and avid chronographer, I was confused by the "science" of this article. Why? Because in all my years of shooting from 11,000 feet to 2000 feet of elevation and from 100 yards to over 2000 yards of distance in temps between 10 degrees to over 100 degrees, I have never seen the humidity change a load with pre-loaded ammo. Not once. Nor have I seen it dramatically change trajectory.

In fact, I can run any bullet I like at any speed I like on any one of my six ballistics programs I have at 1% humidity and then change nothing in the inputs except raising the humidity to 100% and the most significant difference I could get was 2.8" at 1000 yards!! Basically that's undetectable in the real world.

Ok, so usually I hear this humidity "problem" with ammo loaded at the range in a non-controlled environment instead of ammo loaded at home in a controlled environment. In fact, I heard about this problem at the first match I ever shot in. Now, being somewhat open minded, and being new to this game at that time, I thought it went against good science but I wasn't about to dispute who said it because he'd been doing this crazy game for many more moons than I.

But, I have heard it many more times since and now I'm actually reading it in print!

So my question to those who find fault with humidity is this:

Since smokeless powder is NOT hygroscopic, and you have an airtight "container" (at least I hope it's airtight) in which to store your powder until it's ignition (your cartridge), how could humidity change anything? I'm curious.

I mean, what do you feel is changing your load? We have oil down our barrels before the first shot is fired, so water in the barrel can't be it. Even if it was, it wouldn't stay in there longer than the first shot anyway.
Our powder throwers aren't airtight but since powder won't absorb moisture in the air, it doesn't need to be. If there is moisture in the drum from condensation, a few charges would probably get rid of it.

The ballistic programs say that moisture in the air isn't appreciably changing the trajectory of the bullet so that can't be it.

Primers have sealant on them and can be immersed in water for days and still fire so that's not it.

Barrels oscillate how they are going to oscillate regardless of water vapor in the air so that can't be it either.

I'm stumped. I just can't see how humidity would affect our loads. I think what is happening is since the humidity is relative to some degree to the temperature change throughout the day, we are really seeing a result of temperature and correlating it with humidity too. I tune my loads throughout the day based on the ambient air temperature alone. Perhaps this is wrong but it seems to be fairly dependable. At least, to the chronograph it is. I can map out what my load does with any lot of powder throughout the days temperature swings and repeat it with pretty scary consistency at will----especially with N133.

Or is it possible that the link between humidity and mirage is causing the "problem". Perhaps the lighter humidity makes it easier for one to read the resulting mirage and therefore judge the correct hold easier. Or maybe it is interfering with parallax adjustments? I don't know.

It is a scientific meteorological fact that higher humidity will stabilize the air temperature better than low humidity so maybe the quicker changing temperature at low humidity is "putting you in the tune" your gun wants faster? I doubt this one though because it would also go past the tune and out of it quicker too so it wouldn't help you for long.

It would seem to me also that if humidity was the culprit, you could simply get a tuner, load all your ammo at home in a controlled environment and then simply adjust the tuner to compensate for humidity changes. But everyone I've talked to that shoots tuners always talks about changing tuner settings because of temperature or powder lots or something else. I've never heard humidity mentioned in regards to a tuner. Maybe some of the "tuner guys" will chime in. I'm curious...........
 
Goodgrouper

Ever shot N133 in a 6PPC when the humidity dropsinto the 30 percent and below range.??

The big confusion arises when definitions are talked about. When we say that humidity affects 133, that pretains to one thing, the Rifles agging capability. Velocity, ES, SD, pressure, or any other aspect is of no interest. When the humidity drops, and the Rifle goes verticle, you will either do something, or be in the mddle of the pack.

Personally, I do not think you can explain this phenomina by anything other than by actually having the Rifle in competitive tune when the humidity is up, only to see it get really ragged when the humidity falls into that low range. I have talked with powder representatives about this, and they don't get it.

Now, what I mean by humidity is what that little gizmo you get at Radio Shack tells you. Down here in Houston, we get to witness this first hand. We can start the week end shooting in 90 percent, then a front blows through, the air gets really clean and crisp, and the "humidity" drops way down. The Rifle starts acting "cold", and the usual remedy is to up the load untill it tightens back up.

For some reason, the VV powders seem to be one of the few that have this quirk, which leaves me to believe that the culprit is in the retardents they use to controle the burn rate.

You can believe this, or not. But, knowing what to do with 133 when the humidity drops way down is usually what separates those at the top of the score sheet from those at the bottom.........jackie
 
You should probably be asking this on the 1,000 yard forum, since most 100-200 yd. Benchrest shooters load at the range. As to how it works, I am not sure that anyone really knows. I think that the best that you can do is to do some loading and shooting and take good notes. What the fellow was telling you was what his results have been. Why don't you try to duplicate them? Benchrest is somewhat unique in that what we may consider a problem would get lost in the noise of any other kind of shooting. Bottom line, I think that there are too many unknowns and variables for this to be "figured out" in a way that would make loading and tuning, to Benchrest standards, a make the measurements, do the adjustments, and get the same result every time thing. I am not aware of anyone that has done this.
 
goodgrouper said:
Basically that's undetectable in the real world.
Click to expand...


This is Benchrest ....the "real world" doesn't apply here. ( nor do things like "conventional wisdom", and "under normal conditions")

Not trying to be smart here, but when 1st and 2nd place are separated by .0005", if you think adjusting something base on humidity will help ...then you adjust. We do many things that we are almost certain have no effect on tune or performance - but we do them anyway - out of habit or suspicion or even superstition.
 
Last edited:
I used to carry a rabbits foot when shooting smallbore competitions..
It helped...it really did! :D
 
jackie schmidt said:
Ever shot N133 in a 6PPC when the humidity dropsinto the 30 percent and below range.??

The big confusion arises when definitions are talked about. When we say that humidity affects 133, that pretains to one thing, the Rifles agging capability. Velocity, ES, SD, pressure, or any other aspect is of no interest. When the humidity drops, and the Rifle goes verticle, you will either do something, or be in the mddle of the pack.

Personally, I do not think you can explain this phenomina by anything other than by actually having the Rifle in competitive tune when the humidity is up, only to see it get really ragged when the humidity falls into that low range. I have talked with powder representatives about this, and they don't get it.

Now, what I mean by humidity is what that little gizmo you get at Radio Shack tells you. Down here in Houston, we get to witness this first hand. We can start the week end shooting in 90 percent, then a front blows through, the air gets really clean and crisp, and the "humidity" drops way down. The Rifle starts acting "cold", and the usual remedy is to up the load untill it tightens back up.

For some reason, the VV powders seem to be one of the few that have this quirk, which leaves me to believe that the culprit is in the retardents they use to controle the burn rate.

You can believe this, or not. But, knowing what to do with 133 when the humidity drops way down is usually what separates those at the top of the score sheet from those at the bottom.........jackie
Click to expand...



Jackie,
Actually, yes, I have shot in 30% humidity. That is usually what we have here in the high deserts of the Great Basin. I have to specifically plan a day to shoot in high humidity based on forecasts of approaching storm fronts because that is the only time we get more than say 50% humidity.

Don't take what I'm about to say the wrong way. I'm just trying to identify what you're saying in your post. You say that humidity causes you to have to change your load to keep your rifle in "agging capability" when a cold front drops your humidity and that velocities and deviations have nothing to do with it?

You also simply just told me WHAT you do not WHY it is so. I realize you change your loads to stay competitive as do I but I chalk it up to temperature not humidity because there is NO SCIENTIFIC EXPLANATION for why humidity would significantly alter either interior or exterior ballistics! There is, however, boatloads of scientific data supporting the concept of having temperature change the ballistics both interior and exterior.

I agree that the AGG is the supreme determiner of what we do to our guns. But if you don't think that our optimum load for any given match is unrelated to anything going on in the interior of our rifles, you probably ought to reconsider that idea. Fact is, the interior ballistics have everything to do with how well our guns shoot day in and day out and they leave a footprint on the paper AND on the CHRONOGRAPH READING! Were it not so, we would be shooting in the dark! We'd have no way of repeating any kind of accuracy and we would simply have to fumble around and hope we could find something that works. Maybe that's how some guys compete but it's not how I compete. Prior to showing up to any match, I have already mapped out what charges give what kind of accuracy and velocity at what kind of temperature and I can be within half a number on my powder thrower for a starting point for the given temperature at any match I've been to. All I have used to do this is a thermometer. I do not even own a humidity gauge.

Until someone can offer up any kind of scientific proof that humidity does anything at all, I will continue to suspect that we are confusing humidity effects with temperature effects. Has anyone shot a match wherein the temperature stayed constant but the humidity went up or down and actually saw a direct change in the agging capability of their rifle that they know for certain was an absolute result of humidity??
 
Last edited:
ScottD said:
This is Benchrest ....the "real world" doesn't apply here. ( nor do things like "conventional wisdom", and "under normal conditions")

Not trying to be smart here, but when 1st and 2nd place are separated by .0005", if you think adjusting something base on humidity will help ...then you adjust. We do many things that we are almost certain have no effect on tune or performance - but we do them anyway - out of habit or suspicion or even superstition.
Click to expand...

I have come to learn very quickly that a lot of what is done in short range benchrest for group is done on habit, suspicion, and superstition without any factual, scientific understanding. Perhaps that is why you can ask 10 benchrest shooters a question and get 11 different answers back! But that's no reason to not carry a rabbits foot in your pocket!;):)
 
Jim, Think about this

As air temp goes up, air density goes down. A higher temperature reduces the "horsepower" necessary for the bullet to push that column of air out of the barrel in front of it. None of that has any effect on the barrel harmonics, so Velocity goes up, and the tune goes away. Gotta lower the load in an effort to get the bullet to exit the barrel at the top or bottom of it's swing. Relative Humidity plays in, but not near as much as temp. They call it RELATIVE humidity cause it is RELATIVE to the temperature..........A CONSTANT amount of moisture in the air would show as a lower RH at a higher temp than at a lower temp.
Density altitude is calculated by known altitude at the range in question, and the temperature. Water grains per lb. of air can be calculated, but the numbers are in the dirt. I don't watch humidity.......just the temp.
Bryan
 
Answer Me This

Answer me this how would Tony Boyer respond to your question?

One would be hard pressed to second guess Tony's scientific or unscientific real life experiences.
 
Louis J. In James Mock's recent...

Precision Shooting article where he was interviewing Tony and Faye, Tony said he didn't pay any attention to temp or RH...only what the target indicated his load/groups were doing.

Jim
 
You can check with Jim Borden to verify this. He preloaded about 300 rounds for a match, over a period of time in which humidity varied greatly. Since he believes that tune is velocity specific, he adjusted the weight of the charge that he used for each loading session (about 60 rounds) to hit his desired velocity. The total variance in batch charge weights was 1.5 grains. After his shooting buddy challenged the validity of his procedure, he pulled some rounds from each batch and shot groups, using the full range of weights in each. The groups were fine. Put that in your pipe and smoke it.:D You can no longer say that you have never seen any published evidence that humidity has an effect.
 
Jim

Have you thought about the change of barametric pressure, along with the combination of air density, not just humidity.
 
As a possibility, look at these calculation of stability factor taken from JBM Ballistics. I put in average ppc specs and the resulting stability factor seems to be close to the edge.

The next calculation is with all factors constant except the velocity is up by 100 fps. The stability factor goes up. That means that given a certain bullet and atmospheric conditions, faster means more stable.

This suggests that the typical PPC load is close to the edge when speaking of bullet stability, and lower temperatures or lower humidity both of which increase air density and reduce stability factor, may take it over the edge. Increased velocity increases stability factor.

The reason that you, goodgrouper, don't notice this phenomena is that your combo perhaps isn't quite so on the ragged edge of stability.

Untitled-1.gif


Untitled-2.gif
 
Last edited:
bryan said:
As air temp goes up, air density goes down. A higher temperature reduces the "horsepower" necessary for the bullet to push that column of air out of the barrel in front of it. None of that has any effect on the barrel harmonics, so Velocity goes up, and the tune goes away. Gotta lower the load in an effort to get the bullet to exit the barrel at the top or bottom of it's swing. Relative Humidity plays in, but not near as much as temp. They call it RELATIVE humidity cause it is RELATIVE to the temperature..........A CONSTANT amount of moisture in the air would show as a lower RH at a higher temp than at a lower temp.
Density altitude is calculated by known altitude at the range in question, and the temperature. Water grains per lb. of air can be calculated, but the numbers are in the dirt. I don't watch humidity.......just the temp.
Bryan
Click to expand...

Thanks Bryan. You are correct. Another thing you probably know but some may not is that a change of 17 degrees of air temp is equivalent to changing 1000 feet of elevation in air density. So temperature is the thing to watch!
 
TomD said:
As a possibility, look at these calculation of stability factor taken from JBM Ballistics. I put in average ppc specs and the resulting stability factor seems to be close to the edge.

The next calculation is with all factors constant except the velocity is up by 100 fps. The stability factor goes up. That means that given a certain bullet and atmospheric conditions, faster means more stable.

This suggests that the typical PPC load is close to the edge when speaking of bullet stability, and lower temperatures or lower humidity both of which increase air density and reduce stability factor, may take it over the edge. Increased velocity increases stability factor.

The reason that you, goodgrouper, don't notice this phenomena is that your combo perhaps isn't quite so on the ragged edge of stability.

Untitled-1.gif


Untitled-2.gif
Click to expand...


Thanks for your post Tom. I notice that for JBM stability inputs, the temperature and barometric pressure are the only atmospheric inputs needed to calculate the stability factors. There is no box for humidity.

I also notice that JBM states that bullets with stability of 1.3 to 2.0 ensure bullet stability. That must be a typo because the ppc's are 1.03 and above in the example. I run 13.5 twists with 68 grain bullets from 3200 to 3400 depending on what is shooting best and what the barrel wants.
 
So do the humidity "blamers" now lean towards humidity messing up the exterior ballistics more than the interior ballistics or the physical properties of their equipment?

I have seen and have heard about competitors buying the density altitude gauges instead of true humidity gauges. One of my friend's brothers uses a density altitude gauge to jet his race engines in varying places around the western U.S. But these gauges usually just give your corrected altitude and air density. If you do find one that shows Relative Humidity, it doesn't seem to figure it into the result. Why would that be? Is it just something interesting to know perhaps? Maybe telling you how ineffective your sweat is going to be that day? I don't think it's affecting your bullet much.
 
You must log in or register to reply here.
Back
Top