How does humidity affect powder? A new experiment

NamibHunter

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^^^. That’s substituting one source of variability for another IMHO

Don’t want to start a food fight, but what little i remember from chemistry class, the volatile organic compounds (that weird chemical smell you get when you open a container) which is present in the powder kernels will slowly evaporate inside a recently sealed container, while some vapor at the same time gets reabsorbed back into the powder, until equilibrium is reached, and the process stabilizes. This should already happen at the factory. I suspect that leaving a container open for several months will cause the vapor to continue to escape and slowly change the chemical composition of the powder, possibly changing burn rate, but i don’t have the equipment to prove this assertion.

I do know that powder manufacturers ship their product in containers that are often far larger than needed, to maintain a specific “vapor space” above the solid powder. Powders like 4000MR are shipped in containers that have almost 50% more space than “needed”, which increases shipping costs. And if you call them, they really don’t want you to add together 12 one pound bottles (even from the same batch number) into one 8 lbs container and fill it up to the brim. [You have to wonder if a near empty container has a different burn rate than a half full container, because the vapor space is so much different.]

It seems to me that off-gassing might be a problem, so i would not spread out powder in a cake pan and leave it like that for days or weeks… or leave containers open for long periods of time, but i have no scientific proof one way or the other…. maybe keeping a container open for 24 hours is ok, but i would not leave it open for a week.

Would like to hear from a professional chemist with experience in formulating rifle powders!
 
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Yondering

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Thanks! Hope this is helpful to folks.

For the folks who do not have time to read the ‘dissertation’ posted above:

The initial hypothesis that some rounds can soak up moisture appears to be true due to a minority of leaky cases being present in each batch of hand loaded ammo (possibly due to deep scratches inside the neck - have a look with a bore scope, you already have several such cases). [These scratched are caused by powder kernels being forced between case neck and bullet, as the case neck diameter start to enlarge, just before the bullet has time to get going.]

Water content of the powder inside the case affects speed (a proven fact) and therefore will push up your ES some moderate amount: In my first experiment, the moisture soak seemed to add 14 fps to the ES - but that is true only if you are outside the node, it is far less if you are in the flat spot (node) on the speed graph. Wide nodes matter, but it hints that it is not the only effect: Variable neck tension and powder weight differences also drives ES. ‘Leaky’ cases contribute too via humidity changes. Higher neck tension helps to avoid moisture soaking into loader ammo, but it does not cure the problem. Hard to detect unless you drag a milligram scale to the match, which probably is not really practical…

Sealing a case to make it water tight helps and hurts: Humidity soak goes away if you seal every case properly (not so easy in practice), but then neck tension becomes more variable: Sealant acts as a glue. You probably have to use very little and apply it exactly the same on each loaded round to see a net benefit, and not so easy to do by hand. I will not use it in future for target ammo, but will continue to use it for hunting ammo.

‘Bullet weld’ is real and is the dominant effect that dramatically changes bullet grip and therefore ES goed way up, so recommend you load long and reseat the morning of the match.

It might help to transport loaded ammo in two double sealed ziplock bags with a humidor pack inside for humidity control (pick a relative humidity value similar to your reloading room conditions).

Or simply ignore the problem and learn to live with your ES. Trying to control water content of loaded ammo is going yet another 10 feet deeper into the proverbial rabbit hole…. Where does it ever stop?

If you want/need to reduce bullet weld, try testing a batch of ammo without wet tumbling and removal of the carbon in the case neck. I’ve said for a long time that wet tumbling is counter productive for this reason.

Cold weld (not the same thing as galvanic corrosion!) relies on two very clean surfaces in close contact under pressure. In wet tumbled case necks, we have all of those present. The simple solution is to remove the “clean” part of the equation- either by leaving the carbon in the neck, or lube on the cases, etc. Some things work better than others, and as you found some things like your sealant don’t necessarily prevent cold weld.
 
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NamibHunter

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If you want/need to reduce bullet weld, try testing a batch of ammo without wet tumbling and removal of the carbon in the case neck. I’ve said for a long time that wet tumbling is counter productive for this reason.

Cold weld (not the same thing as galvanic corrosion!) relies on two very clean surfaces in close contact under pressure. In wet tumbled case necks, we have all of those present. The simple solution is to remove the “clean” part of the equation- either by leaving the carbon in the neck, or lube on the cases, etc. Some things work better than others, and as you found some things like your sealant don’t necessarily prevent cold weld.

Agree with your comments NOT to over clean the inside of the necks and leaving some carbon in place. I used to run an ultrasonic cleaner, and that over cleaned the 6.5 CM Lapua cases to a shiny state, inside and out. Had significant problems with cold weld if the ammo was left to stand (inside an air conditioned house) for more than a few days.

Once i switched to corn cob tumbling media via a standard vibratory tumbler, and left some carbon in the necks, SDs clearly got better (7-9 fps). Still had the odd round that would stick when reseating (1 in 10 or so), and ES remained a little high (low 30’s). So the problem was mitigated - just not completely solved.

On my new 300 WSM I went a different way: tumble the ADG cases in walnut media for a limited time (60 minutes, via a timer that turns off power to the tumbler), apply Neolube nr 2 to the inside of the neck, and i use HBN coated 225 ELDM bullets. So the bullets are lubricated too. SDs for large 30-40 shot samples came down from 8-10 fps (pretty good) for the 6.5 Creed and the 308, to 4-6 fps for the WSM. ES effectively halved, a very nice improvement. Reseating a box of ammo (40 rounds) that was done 2 weeks ago showed zero sticking bullets. Need to store a box of loaded ammo for 6 months or longer before declaring victory, but this approach is the best i have found so far.

Not sure if it was the Neolube, the HBN bullet coating, or the combo of the two that did the trick, but it worked for me so far.
 
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Yondering

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Agree with your comments NOT to over clean the inside of the necks and leaving some carbon in place. I used to run an ultrasonic cleaner, and that over cleaned the 6.5 CM Lapua cases to a shiny state, inside and out. Had significant problems with cold weld if the ammo was left to stand (inside an air conditioned house) for more than a few days.

Once i switched to corn cob tumbling media and a standard vibratory tumbler, and left carbon in the necks, it clearly got better. Still had the odd round that would stick (1 in 10 or so).

On my new 300 WSM I went a different way: tumble the ADG cases in walnut media for a limited time (60 minutes), apply Neolube nr 2 to the inside of the neck, HBN coated the 225 ELDM’s. SDs (30-40 shot samples) came down from 8-10 fps for the Creed, to 4-6 fps for the WSM. Reseating a box of ammo (40 rounds) that was done 2 weeks ago showed zero sticking bullets.

Not sure if it is the Neolube, the HBN bullet coating, or the combo of the two, but that worked for me.
Roger that. I’m interested to try the HBN but haven’t got around to it yet. Mainly just haven’t taken the time to find a good source. What do you use?

For cleaning, I’ve started adding some carnauba car wax to the corn cob media (which also has Dillon case polish). I use that mixture to remove lube from my sized brass; it does a great job on the outside with just a thin waxy coating left; on the inside it seems to leave a little more of the lube in place. That seems to be working pretty well to eliminate cold welding.
 

NamibHunter

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Roger that. I’m interested to try the HBN but haven’t got around to it yet. Mainly just haven’t taken the time to find a good source. What do you use?

For cleaning, I’ve started adding some carnauba car wax to the corn cob media (which also has Dillon case polish). I use that mixture to remove lube from my sized brass; it does a great job on the outside with just a thin waxy coating left; on the inside it seems to leave a little more of the lube in place. That seems to be working pretty well to eliminate cold welding.

Thanks for the tip. A wax coating should help. New factory cases apparently have a wax coating too.

Well, I order HBN powder direct from David Tubb/Superior Shooting Systems. He adds an anti-copper fouling agent to his blend.

You could order from Amazon, but there have been reports of material being shipped that could be used to badly scratch glass, so not pure lubricant. Either contaminated material, or they simply shipped the wrong chemical. It also need to be of very small particle size, or it won’t impact plate properly on the bullets. The fly-by-night outfits are best avoided, i think.

That said, a buddy of mine uses microLubrol ultrafine grade (<0.5 micrometer), and he gets good results.
 
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NamibHunter

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Just ran an experiment: Skipped the Neolube nr 2 coating on the inside of the necks (with enough black carbon left in the neck from firing the round last time, and still using HBN coated bullets, same load): SD went up from 4-5 fps range to 7.6 fps, for 20 shots. So yes - i am going back to Neolube.

If you go search on Youtube for “Reloading Witch Doctor” you will find a video where he tests no lube, vs Neolube inside the neck only, vs Neolube on bullet plus neck (which got the best groups) in a superb 6PPC bench rest rifle. [Guy has a PhD and has won some BR medals, and works in a scientific research capacity, and he uses proper Statistics (T-test) to detect if there is enough evidence to believe the outcomes of his various experiments. Very dry, but informative. Don’t expect entertainment.]
 
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reubenski

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If you look at his lubed neck groups he has a tendency to drop a round low and right. And the one flyer in the unlubed groups is low and right. It's hard to take that as conclusive evidence.
 

Yondering

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Thanks for the tip. A wax coating should help. New factory cases apparently have a wax coating too.

Well, I order HBN powder direct from David Tubb/Superior Shooting Systems. He adds an anti-coper fouling agent to his blend.

You could order from Amazon, but there have been reports of material being shipped that could be used to badly scratch glass, so not pure lubricant. Either contaminated material, or they simply shipped the wrong chemical. It also need to of very small particle size, or it won’t impact plate properly on the bullets. The fly-by-night outfits are best avoided, i think.

That said, a buddy of mine uses microLubrol ultrafine grade (<0.5 micrometer), and he gets good results.

Thanks for the tips. Agreed on the fly by night places; I'll order some from Tubb.

The neck lubing stuff in your other post makes a lot of sense to me. I'll have to watch those videos for more info when I have time.
Most lubes should act a a "contaminant" to prevent cold welding, but more than that, they can give a huge reduction in static friction, or stiction, which should work in our favor for more consistent neck/bullet friction.
 
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NamibHunter

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I thought this was about HUMIDITY ?

Fair point, sorry!

Not to make excuses, but I have a worry that humidity seeping into cases makes bullet weld worse. But not sure yet.
 
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NamibHunter

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Thanks for the tips. Agreed on the fly by night places; I'll order some from Tubb.

The neck lubing stuff in your other post makes a lot of sense to me. I'll have to watch those videos for more info when I have time.
Most lubes should act a a "contaminant" to prevent cold welding, but more than that, they can give a huge reduction in static friction, or stiction, which should work in our favor for more consistent neck/bullet friction.

Neolube nr 2 is also electrically conductive. Not sure if that matters here or not, but i vaguely recalls that corrosion chemical reactions tend to be electrolytic in nature, so it might have some bearing on its effectiveness. Or not!!

But I do know for sure that i’m WAY out of my depth on the chemistry aspect… Trained professionals need to step in…
 

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I thought this was about HUMIDITY ?
midity


Fair point, sorry!

Not to make excuses, but I have a worry that humidity seeping into cases makes bullet weld worse. But not sure yet.

If that were true then the military would have required specific control of humidity for ammunition storage long ago.
 

NamibHunter

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If that were true then the military would have required specific control of humidity for ammunition storage long ago.

Fair point. Bullet weld is a real phenomena (very badly named), but it is a secondary effect, and not something i would worry about with factory ammo, unless it is stored for 50 years.

If you want to get your ES of 30 fps down to 12-18 fps for shooting at a mile, then taking some basic precautions to mitigate bullet weld can be beneficial. Like seating long and reseating just before the match. Or painting the bullet and the inside neck with Neolube. Not needed for 400 yard 223 ammo.
 

6.5SH

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If that were true then the military would have required specific control of humidity for ammunition storage long ago.
Other than exceptions for some specialty ammo typical "combat" ammo has sealer on the primer and the bullet.
More for it getting wet and staying reliable than humidity changes over time.
 

reubenski

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Fair point. Bullet weld is a real phenomena (very badly named), but it is a secondary effect, and not something i would worry about with factory ammo, unless it is stored for 50 years.

If you want to get your ES of 30 fps down to 12-18 fps for shooting at a mile, then taking some basic precautions to mitigate bullet weld can be beneficial. Like seating long and reseating just before the match. Or painting the bullet and the inside neck with Neolube. Not needed for 400 yard 223 ammo.
What are the health risks associated with Neolube? It has some scary shit on the bottle
 

reubenski

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From the bottle....much more drastic than the document you found on Google

PXL_20220613_035956357.jpg
 

reubenski

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The point is.... I'm not sure I actually want to use it if the warning isn't a massive overstatement
 

6.5SH

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Even powdered graphite is nasty to be around. At least the liquid isn't going to make a cloud of dust.

Glasses, gloves and a solvent respirator are called for when handling it. If we are being honest those were needed for handling Hoppes and every other solvent of yore, but hardly anyone did.
 

reubenski

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Even powdered graphite is nasty to be around. At least the liquid isn't going to make a cloud of dust.

Glasses, gloves and a solvent respirator are called for when handling it. If we are being honest those were needed for handling Hoppes and every other solvent of yore, but hardly anyone did.
Sure. Every lunch I ate at work tasted like shooters choice when I was a sniper instructor. But we've learned better. I now reload with rubber gloves. Low T, cancer, inability to have kids, constant exhaustion. This stuff is running rampant in my organization. I am much more considerate about the way I handle shit these days. Is 2.4 fps of SD worth reloading with a respirator?
 
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secondofangle2

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I’m a pulmonologist and I don’t wear a respirator for any of the aforementioned activities
 

reubenski

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I’m a pulmonologist and I don’t wear a respirator for any of the aforementioned activities
I don't know how to take that. It's like everytime I see a fat doctor, I know he knows better. Does he just like cheese more than he wants to live until he's 90....or ......?
 

MarkyMark007

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not-on-google.shit
Even powdered graphite is nasty to be around. At least the liquid isn't going to make a cloud of dust.

Glasses, gloves and a solvent respirator are called for when handling it. If we are being honest those were needed for handling Hoppes and every other solvent of yore, but hardly anyone did.
than I guess you don't do barbique... there is a 'tones' of powdered graphite... and you not only breathe it, you eat it.

but you are right, powdered graphite is not what you want in your lungs. in china, where they mine grapfite, whole area has damaged lungs and people die very young because of that.
 

Yondering

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than I guess you don't do barbique... there is a 'tones' of powdered graphite... and you not only breathe it, you eat it.

but you are right, powdered graphite is not what you want in your lungs. in china, where they mine grapfite, whole area has damaged lungs and people die very young because of that.

That is not powdered graphite in wood smoke.
 
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secondofangle2

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secondofangle2

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than I guess you don't do barbique... there is a 'tones' of powdered graphite... and you not only breathe it, you eat it.

but you are right, powdered graphite is not what you want in your lungs. in china, where they mine grapfite, whole area has damaged lungs and people die very young because of that.
Where is the pandemic of disabled gun cleaners disabled from Hoppes #9 then?
 

memilanuk

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    So... dragging this back onto the original topic... ;)

    @mc10 question for you: how well sealed do you think an average 'precision' rifle round is? Normal neck tension (say 2-4 thou, no crimp) no sealant just regular 'match' ammo.

    Would it be reasonable to expect the humidity or % moisture content of powder inside a loaded round to remain at, or fairly close to, the ambient conditions at which it was loaded? Assuming that it's just sitting in an ammo box, not physically damaged or exposed to extremes in temperature or moisture ie not left sitting in the sun nor left out freezing or in the rain.
     

    acudaowner

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    you could always try it put some powder in a throw away cup put it outside and leave it for a day or two to see first hand what humidity does should also leave bullets out side and try the same experiment and see if they are affected the same way . send video pics and details on how and what you did , what happened or did not happen , an essay no less than 50,000 words soil samples , blood alcohol levels .
    bullets are not air proof or moisture proof the between the bullet and the copper case is space granted really tiny space but tiny or not moisture will find a way in . if he is experimenting might as well try it as well just to cover everything . id also suggest setting the case standing up in a tiny bit of water to see if water will get in through the case and primer again really tiny but will it be affected or not .
     
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    reubenski

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    So... dragging this back onto the original topic... ;)

    @mc10 question for you: how well sealed do you think an average 'precision' rifle round is? Normal neck tension (say 2-4 thou, no crimp) no sealant just regular 'match' ammo.

    Would it be reasonable to expect the humidity or % moisture content of powder inside a loaded round to remain at, or fairly close to, the ambient conditions at which it was loaded? Assuming that it's just sitting in an ammo box, not physically damaged or exposed to extremes in temperature or moisture ie not left sitting in the sun nor left out freezing or in the rain.
    Have you never shot in the rain? Did all your ammo change drastically when shot in the rain? There's much ado about nothing
     

    reubenski

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    I'm not being wise ass. Even a little bit. But you are pompous beyond tolerable
     
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    Yondering

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    you could always try it put some powder in a throw away cup put it outside and leave it for a day or two to see first hand what humidity does should also leave bullets out side and try the same experiment and see if they are affected the same way . send video pics and details on how and what you did , what happened or did not happen , an essay no less than 50,000 words soil samples , blood alcohol levels .

    :unsure: Why would you see any need to do that with bullets? Lead and copper don't absorb moisture.
     

    NamibHunter

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    So... dragging this back onto the original topic... ;)

    @mc10 question for you: how well sealed do you think an average 'precision' rifle round is? Normal neck tension (say 2-4 thou, no crimp) no sealant just regular 'match' ammo.

    Would it be reasonable to expect the humidity or % moisture content of powder inside a loaded round to remain at, or fairly close to, the ambient conditions at which it was loaded? Assuming that it's just sitting in an ammo box, not physically damaged or exposed to extremes in temperature or moisture ie not left sitting in the sun nor left out freezing or in the rain.

    Only way to convince yourself is to run your own experiment. Not hard to do either. Another person’s post will never be convincing…

    For what it is worth: Several folks have now run the very simple experiment where loaded ammo is left outside for days or week, to see what happens to the weight of each loaded round, and bullet speed when fired. I have tried it twice, and in both cases, a small minority (5-15%) of the loaded rounds lose or gain between 0.04 and 0.1 gn in weight, which can only be caused by two factors a) absorbing or releasing water vapor due to changes in ambient humidity, or b) off-gassing of volatile chemicals from the powder itself (reducing weight).

    Humidity: There is ample evidence, even from the ammo makers themselves, who have published on the topic, that powder humidity affects speed. Powder changes humidity when open to the atmosphere, so don’t leave it in a powder measure hopper, and close the lid tightly. And reload inside the house, not in a shed or a garage.

    Evaporation of volatile organic compounds: There is not much known about this effect (at least not in the literature a reloader would encounter), but it fair to assume that the loss of stabilizer chemicals will have some effect on burn rate. No idea how significant or not this is. Or how fast this occurs. [Powder also slowly degrade chemically over time, but this is a very very slow process (many years to several decades). Not under discussion here.]

    Whatever the mechanism at work here, a small nr of loaded rounds change weight (and i have confirmed they also change speed). You do need a good milligram scale to pick this up, but if you have one, try it and see for yourself.

    The remainder of the ammo appears not to “leak” (or leaks less than 0.02 grains). That inconsistency pushes up the SD by about 1-3 fps (but ES can go way up). Not nothing, but not a train smash either…. You will just shoot over or under your target, maybe 3 to 8x, for one box of 50 reloaded rounds…. For a serious competitor, this will matter. For the rest of us, it is a minor annoyance. [Note that the statistical distribution for MV becomes non-Normal. Two “populations” mixed together, those rounds that leaked and those that did not.]

    “Bullet weld” or whatever the correct terms is, is more significant in my testing. It does get a lot worse with time. Load long and reseat the day you go shoot. [Btw: I think wax coated virgin brass is less susceptible to bullet weld, compared to reloaded brass, but i can’t prove that yet.]. To run this experiment, store some loaded ammo for a year or more.

    My take-away is to control the humidity of your reloading room: Add a dehumidifier if you live in a humid climate. Add a humidifier if you live in a dry desert climate. Try the humidor trick if you like.

    Easy enough to do.
     
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    straightshooter1

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    Why would you do this?
    In the dry desert the dry air sucks moisture out of everything like a dry sponge, doing it rather fast. It not only does it to your body, but it's an issue like with various wood furniture where it'll shrink and crack if not attended to. I've seen my powder loose moisture pretty fast when not put back in it's container as soon as I'm done reloading. And that drying powder DOES burn faster resulting in higher pressures with higher MV's. Even when putting the powder back into it's container, it will have lost enough moister to pull some moisture out of the powder that was left in the container resulting in lower moisture for all the powder in the container as the moister content of the container equalizes. The more extreme the difference between the powder's moisture content to the atmospheric relative humidity the faster the change will take place.
     

    NamibHunter

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    Why would you do this?

    I live on the Gulf Coast, so i don’t need to do this except for one week a year when Houston drops below 35%, but my contention is that as constant as practically possible humidity in your reloading room is better than seeing 15% on a day with clear blue skies with a wind blowing in from the snowy north, compared to 40% when the wind blows in ocean moisture from the south. I just avoid reloading during this time, but i get nose bleeds if the air dries out too much, so invested in a piezo electric humidifier. Works well for noise bleed prevention. Not sure about powder stabilization…. I run the dehumidifier setpoint at 45%. About 10% below what it was before i bought the 2 machines, one per floor.

    My idea is to avoid the situation where the first round you load holds moisture equivalent to 35% (what the bottle was exposed to before you tightly closed it 4 weeks ago), and the last round an hour or two later is closer to 20%, when today’s Relative Humidity is 15% because it is a blue sky day, and the powder is trying to equilibrate to match the ambient conditions. That takes time.

    Powder moisture (while sitting in an unsealed hopper) will slowly ramp up (or down) over several hours. Stabilizing the humidity in your reloading room should help to keep the burn rate very similar between the first loaded round, and the last, completed several hours later. [And keep the door closed so you don’t have to adjust humidity for the entire house.]

    The published graphs show a very big change in burn rate and speed from that kind of humidity change. So either stabilize humidity in your reloading room by dropping it by 10% (if generally on the high side), or raise it if ambient humidity level is normally on the low side (dry climate). Or simply avoid reloading on days when humidity is abnormal…
     
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    reubenski

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    I live on the Gulf Coast, so i don’t need to do this except for one week a year when Houston drops below 35%, but my contention is that as constant as practically possible humidity in your reloading room is better than seeing 15% on a day with clear blue skies with a wind blowing in from the snowy north, compared to 40% when the wind blows in ocean moisture from the south. I just avoid reloading during this time, but i get nose bleeds if the air dries out too much, so invested in a piezo electric humidifier. Works well for noise bleed prevention. Not sure about powder stabilization…

    My idea is to avoid the situation where the first round you load holds moisture equivalent to 35% (what the bottle was exposed to before you tightly closed it 4 weeks ago), and the last round an hour or two later is closer to 20%, when today’s Relative Humidity is 15% because it is a blue sky day.

    Powder moisture (while sitting in an unsealed hopper) will slowly ramp up (or down) over several hours. Stabilizing the humidity in your reloading room should help to keep the burn rate very similar between the first loaded round, and the last, completed several hours later. [And keep the door closed so you don’t have to adjust humidity for the entire house.]

    The graphs show a very big change in burn rate and speed from that kind of humidity change.
    The humidity in my area is consistently low. And powder with a low moisture content performs better in my experience. I have no desire to add humidity to my environment
     

    reubenski

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    In the dry desert the dry air sucks moisture out of everything like a dry sponge, doing it rather fast. It not only does it to your body, but it's an issue like with various wood furniture where it'll shrink and crack if not attended to. I've seen my powder loose moisture pretty fast when not put back in it's container as soon as I'm done reloading. And that drying powder DOES burn faster resulting in higher pressures with higher MV's. Even when putting the powder back into it's container, it will have lost enough moister to pull some moisture out of the powder that was left in the container resulting in lower moisture for all the powder in the container as the moister content of the container equalizes. The more extreme the difference between the powder's moisture content to the atmospheric relative humidity the faster the change will take place.
    This is why you stabilize an entire jug of powder. And then it's consistent rather than trying to constantly fight it. Let it dry. It will stabilize at a point. And then you're GTG. Proceed to load
     
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    straightshooter1

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    This is why you stabilize an entire jug of powder. And then it's consistent rather than trying to constantly fight it. Let it dry. It will stabilize at a point. And then you're GTG. Proceed to load
    Yeah, that sounds like a good idea for where I live and something I haven't tried yet. Guess, I will do that and see how it goes. However, we're entering monsoon season and when it rains hard the RH can rise from 10% to over 90% and take a few days to subside. Indoor humidity isn't affected as much, but it is substantially effected. So, reloading during those times after drying out the powder will need to be a aware and a little cautious.
     

    reubenski

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    Yeah, that sounds like a good idea for where I live and something I haven't tried yet. Guess, I will do that and see how it goes. However, we're entering monsoon season and when it rains hard the RH can rise from 10% to over 90% and take a few days to subside. Indoor humidity isn't affected as much, but it is substantially effected. So, reloading during those times after drying out the powder will need to be a aware and a little cautious.
    Just keep it in the jug after initially stabilizing it. It only takes about 72 hours of airing out for your and mine environments.
     
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    Huskydriver

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    Just keep it in the jug after initially stabilizing it. It only takes about 72 hours of airing out for your and mine environments.

    What are you doing to stabilize it the cooking sheet method or just leaving the lid off?
     

    reubenski

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    What are you doing to stabilize it the cooking sheet method or just leaving the lid off?
    Mainly just pour it all out in a baking pan for three days. Although I have 4lbs of TAC I was able to score off PVA last month. I just unscrewed the lids for a week.
     
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    memilanuk

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    Only way to convince yourself is to run your own experiment. Not hard to do either. Another person’s post will never be convincing…

    For what it is worth: Several folks have now run the very simple experiment where loaded ammo is left outside for days or week, to see what happens to the weight of each loaded round, and bullet speed when fired. I have tried it twice, and in both cases, a small minority (5-15%) of the loaded rounds lose or gain between 0.04 and 0.1 gn in weight, which can only be caused by two factors a) absorbing or releasing water vapor due to changes in ambient humidity, or b) off-gassing of volatile chemicals from the powder itself (reducing weight).
    Whatever the mechanism at work here, a small nr of loaded rounds change weight (and i have confirmed they also change speed). You do need a good milligram scale to pick this up, but if you have one, try it and see for yourself.

    The remainder of the ammo appears not to “leak” (or leaks less than 0.02 grains). That inconsistency pushes up the SD by about 1-3 fps (but ES can go way up). Not nothing, but not a train smash either…. You will just shoot over or under your target, maybe 3 to 8x, for one box of 50 reloaded rounds…. For a serious competitor, this will matter. For the rest of us, it is a minor annoyance. [Note that the statistical distribution for MV becomes non-Normal. Two “populations” mixed together, those rounds that leaked and those that did not.]

    “Bullet weld” or whatever the correct terms is, is more significant in my testing. It does get a lot worse with time. Load long and reseat the day you go shoot. [Btw: I think wax coated virgin brass is less susceptible to bullet weld, compared to reloaded brass, but i can’t prove that yet.]. To run this experiment, store some loaded ammo for a year or more.

    That... actually touches surprisingly closely on what I had in mind when I asked the question. Not so much the leaving the rounds 'outside', if that's what previous testers have done. More so in the context of precision ammo assembled well in advance of a large long-range event, then shipped ahead to a location that has very different temp, BP and RH conditions than where the ammo was originally loaded.

    In a few situations I've known of people who insisted that they got better results fine-tuning their loads locally, on-site, than they did bringing or shipping ammo that was pre-loaded from home. The discussion usually went down a theoretical rabbit hole, about whether the rounds were reasonably well sealed to where the conditions inside were the same as what they were at the loading bench, etc. Generally this ammo would be loaded anywhere from a few weeks to a few months in advance, depending on the venue (national vs. international).

    I'd generally maintained that the people who were advocating loading on-site were unintentionally skewing the results, because they were usually trying to 'get by' with say, 300 pcs of brass - plenty for a local state or regional 2-3 day match with team stages, etc. Not so much for larger national+ level events that run 4-5 days. When they tried loading 'at the range' with their previous recipe... I'm guessing the local temp/humidity played hobb with their load tune. Their response was something along the lines of "you just wouldn't understand" because I shot F/TR instead of F/Open ;)

    I do have some ammo that has been sitting in my air-conditioned (heated/cooled, but not humidity controlled) shop for a couple years. I'd have to look back at my notes to see what exactly the powder charge was originally; it might be interesting to see what it weighs now, on the same scale (FX-120i). I don't *think* I have records detailing the MV average/SD/ES in enough detail that I'd trust it for a representative before/after comparison, though.
     

    MarkyMark007

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    dont mix relative humidity and absolute humidity !!!

    at 0°C at 100% relative humidity you have as much water in the air (absolute humidity) like at 50% relative humidity at ~18°C.


    when you say that you have 50% relative humidity in some room, at higher temperatures you have a lot more water in the air. and probably you can get more water in the powder at higher absolute humidity; imho...
     

    NamibHunter

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    Reviving an old thread:

    I see Vihtavouri powders in stock more frequently now, and they claim “extreme temperature stability” and also claim their powder is “insensitive to humidity changes”.

    Has anybody done any testing with the N500 series of powders (N560, N565, N568, N570) to determine speed difference between powder at say 30 RH compared to 80% RH? Is it any better than say H4831SC…or Retumbo…
     

    Emerson0311

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    Reviving an old thread:

    I see Vihtavouri powders in stock more frequently now, and they claim “extreme temperature stability” and also claim their powder is “insensitive to humidity changes”.

    Has anybody done any testing with the N500 series of powders (N560, N565, N568, N570) to determine speed difference between powder at say 30 RH compared to 80% RH? Is it any better than say H4831SC…or Retumbo…
    Lots of people who aren’t poors have used Vihtavouri powder for years with great success. My experience is just getting started because it was all I could find.
     

    cas6969

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    Currently the heat and humidity in my reloading room is keeping me from doing any reloading, so there's that.