Powder moisture and velocity?

[F Class John]

This was a really great experiment done by the guy over at Chronoplotter with great controls to show the effect of humidity.

How does humidity affect powder?

You may have heard about a relationship between humidity and bullet velocity either in a book, on a reloading forum, or from a crusty benchrest shooter right after saying they get better ES/SD&#821…

chronoplotter.com

 

[Ringostar]

This was a really great experiment done with great controls to show the effect of humidity.

How does humidity affect powder?

You may have heard about a relationship between humidity and bullet velocity either in a book, on a reloading forum, or from a crusty benchrest shooter right after saying they get better ES/SD&#821…

chronoplotter.com

That’s a very interesting article and test. If someone wants to experiment, they can adjust burn rates. If you’d like to try something between 2 powders, eg; 4350 and 4831, you can add or subtract moisture to adjust burn rate.

 

[243winxb]

Keith did a video on this

Is that correct, a difference of 8 feet per second?

 

[RabbitSlayer]

This was a really great experiment done with great controls to show the effect of humidity.

How does humidity affect powder?

You may have heard about a relationship between humidity and bullet velocity either in a book, on a reloading forum, or from a crusty benchrest shooter right after saying they get better ES/SD&#821…

chronoplotter.com

Good article. I didn't think it would change it that much.

 

[Laurie]

I've wondered a bit about this... we all assume that once loaded, the cartridge is essentially a sealed container, with no moisture exchange in or out. But... one has to wonder, if that's so, why do militaries bother sealing their ammo? Granted, those rounds are likely exposed to far worse conditions, and probably over a much longer time, than anything we're realistically concerned about here.

Military ammunition is procured to absolute lowest prices subject to performance standards. If cartridges didn't need sealing, you can be damned sure the procurement agency wouldn't specify such, and the manufacturer wouldn't do it! Moreover, Norma specifically says our type of ammunition is not sealed and is affected by ambient humidity over time. (see below)

This was a really great experiment done by the guy over at Chronoplotter with great controls to show the effect of humidity.

How does humidity affect powder?

You may have heard about a relationship between humidity and bullet velocity either in a book, on a reloading forum, or from a crusty benchrest shooter right after saying they get better ES/SD&#821…

chronoplotter.com

Good stuff.... BUT. The Chronoplotter report relies heavily on the very detailed information and test results in the Norma reloading manual, then omits a key piece of background - that Norma's tests were carried out on ammunition, not stored powder.

Quote:

RH EFFECTS ON THE AMMUNITION
In an effort to understand what will happen and how fast the changes take place, tests were conducted in which ammunition was stored at two RH levels. Two types were used: .38Spcl pistol, loaded with a porous nitrocellulose powder; and 30-06 rifle loaded with Norma 203B powder. [85% nitrocellulose; 7.5% nitroglycerine according to the products characteristics table in the same manual.]

Half of the ammunition lots were stored at 20% RH and the other half at 86% RH. To determine the effect on pressure and velocity, the ammunition was test fired a number of times at over a period of time from 663 to 863 storage days. Had the cartridges been totally sealed or the powder totally insensitive to variations in the RH, after this treatment the differences in pressure and velocity would be expected to be 0. Previously it was shown that the time-pressure curve for a powder change is a function of RH and, since we know that ammunition for shooting and hunting is not sealed, one would expect the properties of the ammunition to change after this treatment. ...................

[Then refers to actual changes shown in Tables 5 and 6 of pressure and velocity changes against storage time in 100 days intervals. 30-06 / 203-B was total 4% MV / 12% pressure changes peaking at c. 400 days storage.]

............... The diagram shows that it took about one year for the moisture content of the powder to to reach equilibrium with the surrounding atmosphere.

I would assume that powder canisters are much better sealed than cartridges in this respect, especially where the opening and cap are small in relation to the can size. If so, there would be limited change in stored powder over time, the exception being the effects of can opening during loading sessions when powder is poured into a measure hopper (and to that powder in the measure before any surplus is returned to the can).

The lessons to me (very likely not others) are:

If buying large cans (3.5kg / 8lb) which will take a long time to use up, decant a usable quantity into a smaller sealed can and use it for a smaller number of loading sessions. (NB This breaks UK Health & Safety Executive powder storage and handling regulations and may well do so in other jurisdictions.)

Recap powder cans tightly immediately after pouring powder out and returning surplus quantities. Likewise, keep the powder measure reservoir capped during sessions and return the surplus ASAP to the manufacturer's can after charging cases.

In extreme humidity environments, use dehumidifiers etc during ammunition loading (and ammunition storage if feasible) as a higher priority than in unused powder stores.

 

[memilanuk]

@Laurie i just secured a copy of the Norma manual (had to order it from a reloading shop in the UK, ouchie) but haven't had a chance to really dig into it.

 

[barefooter56]

A couple months ago I tested a 223, 25.5 gr of TAC, with 53 gr vmax, and for 25 shots the average was 3293 at 97 degrees. I then loaded a couple hundred.

Last weekend I shot 50 of them and the average was 3360 at 65 degrees. I was expecting slower not faster! I had opened a fresh 8lb jug. It was a couple weeks after initial testing till loading the rest. The loaded rounds sat maybe 4 weeks. I live in las vegas, so the humidity is crazy low. Can the powder drying out really change the velocity that much? I did not let it sit in the hopper between loading sessions.

My other theory is neck weld? I graphite lubed before the mandrel, but not before seating. Its new brass

Powder dries out = faster burn rate. Powder collects moisture = slower burn rate. Unless you use a sealer around the inside of the neck and in the primer pocket your powder can dry out in the cartridge case. Storing your cartridges in a military ammo can with a good seal MAY stop/reduce this effect.

 

[Doom]

Military ammunition is procured to absolute lowest prices subject to performance standards. If cartridges didn't need sealing, you can be damned sure the procurement agency wouldn't specify such, and the manufacturer wouldn't do it! Moreover, Norma specifically says our type of ammunition is not sealed and is affected by ambient humidity over time. (see below)



Good stuff.... BUT. The Chronoplotter report relies heavily on the very detailed information and test results in the Norma reloading manual, then omits a key piece of background - that Norma's tests were carried out on ammunition, not stored powder.

Quote:

RH EFFECTS ON THE AMMUNITION
In an effort to understand what will happen and how fast the changes take place, tests were conducted in which ammunition was stored at two RH levels. Two types were used: .38Spcl pistol, loaded with a porous nitrocellulose powder; and 30-06 rifle loaded with Norma 203B powder. [85% nitrocellulose; 7.5% nitroglycerine according to the products characteristics table in the same manual.]

Half of the ammunition lots were stored at 20% RH and the other half at 86% RH. To determine the effect on pressure and velocity, the ammunition was test fired a number of times at over a period of time from 663 to 863 storage days. Had the cartridges been totally sealed or the powder totally insensitive to variations in the RH, after this treatment the differences in pressure and velocity would be expected to be 0. Previously it was shown that the time-pressure curve for a powder change is a function of RH and, since we know that ammunition for shooting and hunting is not sealed, one would expect the properties of the ammunition to change after this treatment. ...................

[Then refers to actual changes shown in Tables 5 and 6 of pressure and velocity changes against storage time in 100 days intervals. 30-06 / 203-B was total 4% MV / 12% pressure changes peaking at c. 400 days storage.]

............... The diagram shows that it took about one year for the moisture content of the powder to to reach equilibrium with the surrounding atmosphere.

I would assume that powder canisters are much better sealed than cartridges in this respect, especially where the opening and cap are small in relation to the can size. If so, there would be limited change in stored powder over time, the exception being the effects of can opening during loading sessions when powder is poured into a measure hopper (and to that powder in the measure before any surplus is returned to the can).

The lessons to me (very likely not others) are:

If buying large cans (3.5kg / 8lb) which will take a long time to use up, decant a usable quantity into a smaller sealed can and use it for a smaller number of loading sessions. (NB This breaks UK Health & Safety Executive powder storage and handling regulations and may well do so in other jurisdictions.)

Recap powder cans tightly immediately after pouring powder out and returning surplus quantities. Likewise, keep the powder measure reservoir capped during sessions and return the surplus ASAP to the manufacturer's can after charging cases.

In extreme humidity environments, use dehumidifiers etc during ammunition loading (and ammunition storage if feasible) as a higher priority than in unused powder stores.

Thanks for posting this information. Unfortunately there is a lot of "data" and "testing" that has been done that forcibly modifies the moisture content (powder does not have humidity) of powder and its effect on velocity. There is little to no test data that shows how powder moisture changes with time and ambient humidity. Powder takes time to change its moisture level in relation to air because the transfer mechanism occurs only on the surface and the moisture is contained throughout the kernel. In normal storage and loading most of the powder resides in a packed column that does not allow free movement of air. When poured kernels are exposed to free air for only fractions of a second the change in moisture is minimal and at the surface. Powder in a sealed but non hermetically sealed container does not magically come to equilibrium with the air outside the container. Even with changes in barometric pressure and temperature very little air is exchanged compared to the air in the container. The HDPE container itself essentially allows no movement of air or moisture (it does, but the amount is extremely small). The physics and chemistry involved is complex. Suffice it to say that the effects of humidity variations in normal storage and proper handling of powder can be measured in days or weeks and years, not minutes or hours.

The amount of moisture in the air in an 8LB powder container is extremely small compared to the moisture in the powder. Air at 70 degrees and 99% humidity in an 8lb container of has about 0.00018 lbs of water. One pound of powder of at 1% moisture has 0.01lb of moisture (water). If the powder were to absorb all of the moisture in the air (which it would not) in that container it would only increase the moisture content of the powder to 1.018%. If the powder had been in equilibrium at 70 degrees F and 50% Relative Humidity it would have absorbed only 0.00009 lbs and the powder moisture would have increased to only 1.009%.

There are places where longterm storage in unconditioned spaces can have a very long term effect. One such case is Las Vegas.

If stored in this environment in a non hermetically sealed container the powder would ultimately acclimate to equilibrium at approximately 31% but the process would take years in an unopened container.

Another location of interest might be Seattle.



Here the powder would ultimately reach equilibrium with about 73%.

So what about Denver CO?






This humidity data is from https://weather-and-climate.com/

 

[BoydAllen]

Years back, when Precision Shooting Magazine was printed on non-glossy paper in B&W, there was a very good article published on the effect of moisture levels of several powders. the thing that was brilliant about the test was that the powder was measured into cases from a freshly opened jug, and then exposed to wet or dry conditions. The difference from the driest to the wettest was over 200 FPS. The really good thing about this test was that any of us could do it, with no special equipment other than a chronograph. I scanned the article, and have those files.

 

[BoydAllen]

How Travel Humidity Changes Can Affect Ammo Performance « Daily Bulletin

This article comes from the Bryan Litz Ballistics Facebook page. That page offers valuable tips on ballistics, marksmanship, and precision reloading, with updates nearly every day of the year. One recent post relates to velocity changes that can occur when traveling away from home.

bulletin.accurateshooter.com

 

[K Hope]

Thanks for posting this information. Unfortunately there is a lot of "data" and "testing" that has been done that forcibly modifies the moisture content (powder does not have humidity) of powder and its effect on velocity. There is little to no test data that shows how powder moisture changes with time and ambient humidity. Powder takes time to change its moisture level in relation to air because the transfer mechanism occurs only on the surface and the moisture is contained throughout the kernel. In normal storage and loading most of the powder resides in a packed column that does not allow free movement of air. When poured kernels are exposed to free air for only fractions of a second the change in moisture is minimal and at the surface. Powder in a sealed but non hermetically sealed container does not magically come to equilibrium with the air outside the container. Even with changes in barometric pressure and temperature very little air is exchanged compared to the air in the container. The HDPE container itself essentially allows no movement of air or moisture (it does, but the amount is extremely small). The physics and chemistry involved is complex. Suffice it to say that the effects of humidity variations in normal storage and proper handling of powder can be measured in days or weeks and years, not minutes or hours.

The amount of moisture in the air in an 8LB powder container is extremely small compared to the moisture in the powder. Air at 70 degrees and 99% humidity in an 8lb container of has about 0.00018 lbs of water. One pound of powder of at 1% moisture has 0.01lb of moisture (water). If the powder were to absorb all of the moisture in the air (which it would not) in that container it would only increase the moisture content of the powder to 1.018%. If the powder had been in equilibrium at 70 degrees F and 50% Relative Humidity it would have absorbed only 0.00009 lbs and the powder moisture would have increased to only 1.009%.

There are places where longterm storage in unconditioned spaces can have a very long term effect. One such case is Las Vegas.
View attachment 1608370View attachment 1608370View attachment 1608370
If stored in this environment in a non hermetically sealed container the powder would ultimately acclimate to equilibrium at approximately 31% but the process would take years in an unopened container.

Another location of interest might be Seattle.

View attachment 1608371

Here the powder would ultimately reach equilibrium with about 73%.

So what about Denver CO?

View attachment 1608384




This humidity data is from https://weather-and-climate.com/

Could you please clarify: Is the humidity / moisture phase rate change the same in a packed column versus a drop tube? And, in what way does adsorbed moisture differ from absorbed moisture with respect to performance?

 

[6.5 forever]

I once read that a shooter preferred one pound containers vs eight pounders. Due to the eight pounders being opened, poured into the dump and the excess being returned to the jug several times. Any thoughts on this?

 

[Doom]

How Travel Humidity Changes Can Affect Ammo Performance « Daily Bulletin

This article comes from the Bryan Litz Ballistics Facebook page. That page offers valuable tips on ballistics, marksmanship, and precision reloading, with updates nearly every day of the year. One recent post relates to velocity changes that can occur when traveling away from home.

bulletin.accurateshooter.com

Boyd,

Brian is a very knowledgeable engineer and I can't argue with what he is saying about moisture and velocity, but what he and most others miss, and is probably missing from the Precision Shooting Magazine article is any analysis of the transport mechanisms that are required to move the moisture as I described in my post. There is no argument that adding or decreasing moisture level in smokeless power does change burn rate and energy as so many have demonstrated.

If powder did respond to humidity changes instantaneously or as rapidly as many assume powder manufactures and suppliers would have handling and storage recommendations that addressed the issue.

Could you please clarify: Is the humidity / moisture phase rate change the same in a packed column versus a drop tube? And, in what way does adsorbed moisture differ from absorbed moisture with respect to performance?

The forced movement of air through a packed column or movement of a kernel through the air as in a drop tube does change the rate as fresh moisture laden or deficient air is exposed to the surface of the kernel. While some different transfer phenomena are at play it is akin to normal industrial powder drying where the particle is dried in a moving air stream. However the amount of time spent in this condition (drop tube or pouring from container is extremely small in relation to the rates of exchange. Also remember that the transfer can go both ways. I'm not sure as to what is being used concerning different moistures. Moisture has two primary effects on combustion. First, it acts a a diluent in the combustion process. that is it takes energy to convert it from a liquid to a gas and more energy to raise its temperature along with the combustion products, hence lowering the peak temperature. It also dilutes the amount of active nitrogen compounds in a given weight of powder. Higher moisture less nitrocellulose/nitroglycerine and vice versa.

I once read that a shooter preferred one pound containers vs eight pounders. Due to the eight pounders being opened, poured into the dump and the excess being returned to the jug several times. Any thoughts on this?

In theory this logic seems to make sense from a theoretical standpoint. But the real question is does it make any observable difference in the real world? It would be an interesting experiment to do in a laboratory environment.

 

[K Hope]

Boyd,

Brian is a very knowledgeable engineer and I can't argue with what he is saying about moisture and velocity, but what he and most others miss, and is probably missing from the Precision Shooting Magazine article is any analysis of the transport mechanisms that are required to move the moisture as I described in my post. There is no argument that adding or decreasing moisture level in smokeless power does change burn rate and energy as so many have demonstrated.

If powder did respond to humidity changes instantaneously or as rapidly as many assume powder manufactures and suppliers would have handling and storage recommendations that addressed the issue.


The forced movement of air through a packed column or movement of a kernel through the air as in a drop tube does change the rate as fresh moisture laden or deficient air is exposed to the surface of the kernel. While some different transfer phenomena are at play it is akin to normal industrial powder drying where the particle is dried in a moving air stream. However the amount of time spent in this condition (drop tube or pouring from container is extremely small in relation to the rates of exchange. Also remember that the transfer can go both ways. I'm not sure as to what is being used concerning different moistures. Moisture has two primary effects on combustion. First, it acts a a diluent in the combustion process. that is it takes energy to convert it from a liquid to a gas and more energy to raise its temperature along with the combustion products, hence lowering the peak temperature. It also dilutes the amount of active nitrogen compounds in a given weight of powder. Higher moisture less nitrocellulose/nitroglycerine and vice versa.

In theory this logic seems to make sense from a theoretical standpoint. But the real question is does it make any observable difference in the real world? It would be an interesting experiment to do in a laboratory environment.

When I shot Group I was way more concerned with powder’s moisture content than I am today. Loading at the range and dealing with all the weather changes during the day is best dealt with by the masters. From what I have seen nitrocellulose has a natural affinity (H-Bond) to water molecules; it picks up moisture fast and loses it relatively slowly. Moisture pickup is enhanced by high Relative Humidity, Dew Point Temperatures and powder temperature. NC has a crystalline / amorphous makeup whereby gained vapor or moisture will be bound or unbound. The bound moisture in the NC’s fibrous makeup limits moisture loss and the unbound transport is thermal. Field environment drying is not the same as what is used in the manufacturing process.

Agreed: The physics and chemistry is complex.

 

[Doom]

When I shot Group I was way more concerned with powder’s moisture content than I am today. Loading at the range and dealing with all the weather changes during the day is best dealt with by the masters. From what I have seen nitrocellulose has a natural affinity (H-Bond) to water molecules; it picks up moisture fast and loses it relatively slowly. Moisture pickup is enhanced by high Relative Humidity, Dew Point Temperatures and powder temperature. NC has a crystalline / amorphous makeup whereby gained vapor or moisture will be bound or unbound. The bound moisture in the NC’s fibrous makeup limits moisture loss and the unbound transport is thermal. Field environment drying is not the same as what is used in the manufacturing process.

Agreed: The physics and chemistry is complex.

You sound like a Chem E! My reference to drying in an air stream was not meant to imply that it is used to dry smokeless powder but more of a general industrial processes.

 

[Someone online]

I would like to see a test of loaded rounds and compare how storage in various humidity environments and lengths of time affect their velocity due to absorption of water.

 

[Laurie]

I would like to see a test of loaded rounds and compare how storage in various humidity environments and lengths of time affect their velocity due to absorption of water.

That's precisely what the detailed Norma exercise covered in its No.2 Reloading Manual does.

 

[Jeff Porter]

Nomex undies on …. I have dried powder at 105 F for four hours in a food dehydrator to get consistent moisture levels and seen velocity increase 100-200 fps over non dried from the same jug ( 30gr H4895 6BRA ) . Also makes lot to lot variability less extreme.