Water soaked powder charge

Hygroscopic

Bob,

I recently read a shooter describing smokeless powder as highly hygroscopic. I believe cellulose is highly hygroscopic but smokeless powder is not cellulose, it is cellulose nitrate. I also recently looked for the hygroscopic nature of various materials but could find nothing. Please let me know if you know of such information.

I think smokeless powder is hygroscopic to some degree but not highly hygroscopic. Here is a little test: place a granule of extruded smokeless powder in the jaws of a fingernail clipper and cut the granule in half. Use your judgment and experience, based on cutting the granule, what material is that granule of smokeless powder most like?

If you are concerned with humidity absorption into your smokeless powder, test your powder to see whether it gains weight or losses weight and to what degree. It will likely vary from powder to powder and from lot to lot and will also vary with the atmospheric dew point.

Yesterday I loaded 34 rounds for a 600 yard match to be held Saturday at the James Howard Prince Memorial Gun Range, located between Pioneer and Goodwill, Louisiana. My load is my 6mmx64 with RWS brass, Wolf primers, 55 grains Retumbo with a 115 grain Berger VLD Match, 0.011 ITL at a muzzle velocity of 3269 f/s out of a 33" long Krieger, 0.237" bore and 7" twist. I left one charge out and over a period of 20.92 hours it gained 0.06 grains weight. Based on the results of 1.36% water absorption into 54 grains H1000, I estimate a velocity loss of about 0.8 f/s for the 55 grain load of Retumbo exposed for 1 hour to moisture absorption.

The description of 80% humidity is not adequate, you must also state the temperature. Dew point is a better method of describing humidity, R.H. is a poor method. An R.H. of 30% at 80 F is more humid than a R.H. of 100% at 40 F. Go to Wikipedia and read about R.H., especially look at the chart near the bottom of the page that plots the humidity in terms of water vapor per kg of air versus temperature for 50% and 100% R.H.

Henry
 
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12 Match cartridges weighed

Rich & Bob,

When I weighed the Retumb powder charge as described in my last post above, I also weighed (12) 6mmx64 cartridges a little earlier. They are loaded with 55 grains Retumbo and seated intentionally in necks with powder residue on the inside surface of the necks. These are part of the cartridges for the 600 yard match tomorrow near the towns of Goodwill and Pioneer, Louisiana:

At 10:16 hrs., 6/15/11, the (12) cartridges weighed 4469.14 grains and today
at 14:00 hrs., 6/17/11, the same (12) cartridges weighed 4469.14 grains. Thus they did not loose or gain any weight over 51.73 hours. During that period of time the temperature in my shop, where the cartridges were kept and weighed, averaged around 84 F with dew points outside ranging from the upper 60s to the low 70s.

The brass used in the cartridges, as stated above, is RWS and in addition the 6mmx64 brass was formed from full length RWS 270 Win. brass with no shortning of the original brass. Also as stated before, the bullet is the Berger 115 grain Match and primers are by Wolf.

Henry
 
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I corrected some of the spelling or typographical errors above.

One shooter suggested making a test, similar to the test described above, using a match rifle. I would love to do that but do not have time now, maybe later. Here are some suggestions one might consider if the test is done:

Use a chronograph with at least 8 feet of screen spacing, preferably greater, to reduce bullet location detection error by the sky screens. A chronograph with an 8-foot sky screen spacing will have a maximum velocity error of probably less than 3 f/s. (Placing two identical and very carefully setup chronographs inline, both having the same sky screen spacing and shooting a ten shot string across both simultaneously can give a good idea of error due to sky screen bullet location detection for those chronographs.)

Take velocity readings for at least 10 rounds for dry loads and 10 rounds for wet loads (25 rounds might be a good choice if the tester is to compare the average group size of five 5-shot groups of dry loads against five 5-shot groups of wet loads). Calculate the standard error for each velocity set to check that there is a significant velocity difference between the dry load and wet load velocity averages.

For the dry load of the test above the standard deviation, SD, was 9 f/s. The standard error is the SD/sqrt(n) or 9/sqrt(10) = 2.8 f/s, “n“ being the number of rounds fired to obtain the average velocity. The standard error for this test is an estimate of the significance of the dry load velocity average. The standard error in the dry load average of the test above indicates that the 10-shot sample average lies within 2.8 f/s of an average of a very large number of rounds fired from the same load.

Choose a powder for a test and test a sample of dry powder for weight gain or loss for a day and in the area where cartridge loading is to take place, by weighing the powder precisely, placing it in an open dish for a day then weighing again. This procedure will give the tester an idea of the state of the test powder and a basis of comparison to a similar test described below.

Preparing the wet charges: One might add water to the powder to avoid the problem of removing surface water from powder that has been soaked under water. If twenty five rounds of a load of 30 grains of dry powder with 0.4% water absorbed by the powder is to be tested, the tester could set aside about 1000 grains of dry powder, weighed precisely, then place it in a bottle. Using a miniature sprayer, spray the 4 grains water into the bottle in stages, while mixing the powder and water between each stages of spraying. Then tumble the bottle of powder in a tumbler for several hours. Let the bottle with wet powder set for several days before proceeding with the test. (0.4% water is a considerable amount of water to add to powder but will likely give a considerable difference in average velocity of dry charges compared to wet charges.)

After the wet powder has “aged”, weigh the wet powder, outside of the bottle in which the wet powder was prepared, to determine the actual gain in water. Then weigh a small sample of the wet powder to be set out in the open during the loading of the wet charges into cartridges. Weigh the sample again to determine if it has gained or lost weight during the wet powder loading procedure.

If the dry powder load, to be compared to the wet powder load is 30 grains and the water gain of the wet powder is actually 0.4%, then the wet powder loads must weigh 30.12 grains each in order that the wet powder charges include 30 grains dry powder plus 0.4% or 0.12 grains water.

Then if the twenty-five dry powder loads were loaded first, shoot the test, preferably at constant temperature conditions with no wind. An indoor range would be useful.

In the test, if powder charges are thrown instead of weighing, one could weight the dry and wet charges poured into the volumetric powder measure before and after each twenty-five set of loads were loaded in order to determine the average weight of dry and wet charges loaded.

An alternative to the test above, and probably safest, instead of adding water to the 1000 grains of powder to prepare it as wet powder: One might let the 1000 grains of powder set out in the open for several hours or the time interval the powder is exposed to the atmosphere during a match, allowing the powder to gain or loose weight and then compare it with “dry” powder by group size and velocity average. The alternative test is very likely the most realistic test but the difference in velocity between the "dry" charge loads and "wet" charge loads in the alternative test is likely to be smaller than many chronographs can detect.

Henry
 
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Henry one more thing to consider though I dont know how it could be done. And it probably is not relevant for long range like it is for short, but find some way of detecting the volume change. Short rangers throw charges which makes it a volume issue. I dont know but having the same weight of powder in a long range case might show little difference but if it does the question I would ask is it just the water or could it also be the volume the powder takes up in the case,,long or short range.
 
Vern,

If the water served to just take up part of the free volume in the cartridge cases and absorbed no energy from the burning powder, then the velocity would be increased slightly. But we know the water absorbs energy to heat it to the boiling point, boil the water then heat the steam to about 4000 F. The steam would likely dissociate into hydrogen and oxygen gases, taking more energy. I believe that the hydrogen would not dissociate into a plasma and I am not sure if the oxygen would dissociate into a plasma. But it is safe to say the water would absorb a significant amount of energy produced by the burning powder, slowing the burning rate of the powder and making less energy available to drive the bullet. That, resulting in a lower muzzle velocity for the wet charge, which the test showed.

Henry
 
Thank you Henry.
I do understand that even from your test results.
I guess I just didint make myself clear on the volume issue.
But thanks again for all the hard work and sharing your information.
 
Vern,

I did get the idea that you were talking about the thrown volumetric charges versus weighed charges issue. If that is the case then that is a totally different question and I believe would take a tremendous amount of testing, testing that likely would not settle the issue in many folk's minds.

Henry
 
Additional information on propellants and water soaked test

I. Propellants (This section has been placed under the post about Manufacture of Smokeless Powder.):

Additional information about the constituents of propellants M2 and M5 plus a single base IMR propellant.
----------------------------------Information within brackets, [ ], by HBC.

From Interior Ballistics of Guns, page 310, Table 2
Edited by
Herman Krier and Martin Summerfield

Progress in Astronautics
And Aeronautics

Martin Summerfield
Series Editor-in-Chief

Volume 66

ISBN 0-915928-32-9

Copyright 1979 by
American Institute of Aeronautics and Astronautics

Constituent--------------------M2----------------- M5-----------------IMR [1)]
Nitrocellulose (NC), %-----77.45---------------81.95----------------100.00
% nitrogen in NC-----------(13.25)--------------(13.25)-------------(13.15)
Nitroglycerin, %-------------19.50---------------15.00----------------…
Barium nitrate, %------------1.40-----------------1.40-----------------…
Potassium nitrate, %--------0.75------------------0.75-----------------…
Potassium sulfate, %--------…-------------------…-------------------1.00 a
Dinitrotoluene, %----------- …------------------- …------------------- 8.00 b
Diphenylamine, %-----------…-------------------…-------------------0.70
Ethyl centralite, %-----------0.60---------------- 0.60-----------------…
Graphite, %-------------------0.30---------------- 0.30-----------------…
Ethyl Alcohol(residual), %-----2.30-----------------2.30-----------------1.50
Water (residual), %--------- 0.70-----------------0.70-----------------1.00
Isochoric flame temp.
-------------- Tv, K----------3319-[5515 F]----3245 [5382 F]----2835 [4643 F]
Unoxidized carbon, %------0--------------------0---------------------2.7
Combustibles, %------------ 47.2-----------------47.4-----------------59.2
Heat of explosion, cal/g----1080 [4521 J/g]----1047 [4383 J/g]----868 [3633 J/g]
Density, g/cm3---------------1.65-----------------1.65-----------------1.62 [density of solid NC]

a) Added. b) Glaze added.
[Isochoric: A constant volume process as in a bomb calorimeter.]
[1) It was not stated which IMR propellant, (possibly IMR 4895)]







II. Additional data on Water Soaked Test (This section has been placed in the post above, about the test.)

The information below is about the ten “dry” charges and ten “wet” charges of H1000:

---------------------------------------------------------------------------------------------Dry charge component of
---------------------------------------------------------------------------------------------“wet” charges plus water,
Order of----------------Dry” charges,-----------Dry charge component of----------------------seconds before loading,
Fire---------------------grains---------------------“wet” charges, grains----------------------grains

--1-----------------------54.02---------------------------54.00-----------------------------54.76
--2-----------------------54.00---------------------------54.02-----------------------------54.74
--3-----------------------54.02---------------------------54.00-----------------------------54.74
--4-----------------------54.02---------------------------54.00-----------------------------54.74
--5-----------------------54.00---------------------------54.02-----------------------------54.76
--6-----------------------54.02---------------------------54.00-----------------------------54.70
--7-----------------------54.02---------------------------54.00-----------------------------54.74
--8-----------------------54.00---------------------------54.00-----------------------------54.74
--9-----------------------54.02---------------------------54.00-----------------------------54.74
--10----------------------54.02--------------------------54.01-----------------------------54.75
 
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Powder exposure test in BR-30 and ctg. Weight change test over 11 days

PART I, H1000 in BR-30 powder measure:

A BR-30 powder measure was locked in the dump position and a 3278.22-grain charge of H1000 powder (same lot as in “water soak test”) was poured into the powder hopper, inside my shop at a temperature of 82 F. The tight sealing hopper cap was immediately installed and the powder measure was taken outside at 11:26 A.M,. 7/1/2011 and placed in its normal vertical position on a screen top, metal patio table, located under the patio roof. Outside temperature was 92 F at a dew point of 68 F (46 % R.H. @ 92 F).

Four hours fifty-two minutes later the BR-30 measure was brought inside the shop and the powder charge immediately weighed at 3277.02 grains, thus the powder, inside the closed BR-30 measure lost 1.20 grains or 0.037 % by weight. Outside conditions at the end of the test were 95 F at a dew point of 65F (37 % R.H. @ 92 F).

The elastimer hopper cap sealed tightly and the clear plastic hopper had been previously cemented, with epoxy, to the metal powder measure housing to prevent powder granules from lodging between the bottom of the plastic hopper and the metal housing of the powder measure. Thus, it appears the vapors escaping from the powder charge, escaped through the small clearances between the metal parts of the powder measure and the measure housing.

At the end of the test, the 3277.02 grains of H1000 was poured into a separate container in order not to mix it with the fresh powder in the 8-pound jug.


PART II, H1000 in BR-30 powder measure (same test above but with hopper open to atmosphere):

With the BR-30 hopper open, a piece of aluminum window screen covered the open hopper, with a 1x6 wood plank 1.1” above the open hopper. The BR-30 with a fresh charge of 3425.02 grains H1000 powder (same lot as in “water soak test”) was placed in the same location as described for Part I above. The powder was exposed to the atmosphere at 11:56 A.M., 7/2/2011 at an outside air temperature of 91 F and a dew point of 65 F (37 % R.H. @ 91 F).

After exposure to the atmosphere for 4 hours and 58 minutes, the BR-30 measure with H1000 was taken inside my shop and the powder weighed at 3422.34 grains. Thus, the charge of powder in the BR-30 lost 2.68 grains, or 0.078 % by weight, inside the BR-30 measure with the powder hopper top removed. Outside conditions at the end of the test were 95 F at a dew point of 64 F (36 % R.H. @ 95 F).





RETUMBO, weight change test:

Seventy rounds were loaded with 55 grains Retumbo, Wolf primers, 115-grain Berger VLD Match bullets, RWS brass in a 6mmx64 cartridge for a 1000-yard match to be held in two weeks. The cases were full length sized, primer pockets reamed and inside of necks left with powder fouling remaining from the last firing of the cases.

Sixty cartridges were set aside to be weighed in five groups of twelve cartridges per group. The five groups of twelve cartridges are to be kept unmixed in order that the group weights determined on 7/3/2011 and 7/14/2011 can be compared as well as comparison of the total.

Group No…………FIRST WEIGHING………………………………SECOND WEIGHING
………………….…13:00 hrs., 7/3/2011.……………………………...16:00 hrs., 7/14/2011

1.………………………4470.46 gr……………………………….........4470.40 gr.
2.………………………4469.34 gr……………………………….........4469.30 gr.
3.………………………4473.52 gr……………………………….........4473.50 gr.
4.……………………….4469.20 gr……………………………….........4469.14 gr.
5.……………………….4474.12 gr,……………………………............4474.04

Total………………….22,356.64 gr………………………………........22,356.38 gr.


Thus, in 11-days, 3-hours the 60 cartridges lost 0.26 grains weight for an average weight loss of 0.0043 grains per cartridge.

Checked humidity level in shop with sling psychrometer at 15:33 hrs., 7/7/11 after a small AC had been running since around 9:00 hrs: 80 F dry bulb, 67 F wet bulb for a dew point of 60 F and R.H. of 51% at 80 F. At that time, outside conditions was 97 F at a dew point of 72 F.


Henry
 
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Thank you Mr. Childs for starting this thread and posting your studies.


I find this subject fascinating and have read a fair amount on it; most of which is a way over my head but, I enjoy trying to learn how things work. I have a couple of questions.


I am having somewhat of a hard time seeing how small amounts of moisture picked up during the day can through heat of vaporization and its relation to energy released have that much of an impact.


The energy of a powder is determined by the formulation/composition and, is primarily a function of the flame temperature (Arrhenius relationship). Single-base powder compositions use nitrocellulose (85-98 %) as their sole energetic material and a blend of various additives, which from what I have read are concentrated more along the outside surfaces. I believe nitrocellulose itself to be a hydrophobic material but I am not so sure on all the different additives and, any water absorption from humidity or direct wetness would at best be a diffusion-controlled process.


Do you think it is possible considering the load density used that - hydration along with relatively elevated ambient temperatures of the surface layers of such a surface could produces a volume expansion acting similar to a surfactant or plasticizer; allowing closer proximity and increasing bonding strength, thereby slowing burn rate ignition and the propagation of the flame front?


Thanks

Ken
 
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Added water slows burning rate

K Hope,

In the test, stated above, the average water added to each charge was 1.36% by weight. Part of that 1.36% was likely water on the surface of the propellant granules. That is a substantial amount of water, as other tests performed and listed above indicate. Some propellants lost weight and some gained weight, in those testes conducted about five years ago.

I have been told by a reliable source that at least one smokeless powder manufacturer adds water to lots of powder in order to reduce the burning rate. I think the 7+ % velocity loss in the wet load, in the test above, is due both to the reduction of the burning rate of the wet charges and the loss of energy to latent heat of vaporization and likely energy lost in dissociation of the hydrogen and oxygen molecules at high temperatures as the powder burned.

I don't have any data, other than my tests, on the hygroscopic nature of single, and double base smokeless powders. The powder manufacturers could tell us but that is unlikely.

After posting this reply, I will add the final weights obtained in weighing the sixty 6mmx64 cartridges in the post just above your questions. Over a period of 11 days the 60 cartridges lost 0.26 grains total or 0.0043 grains per cartridge.

Henry
 
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Thank you Sir for your reply and, looking forward to your next post.


I think I have a grasp on a few key aspects of powder makeup and the physical processes that occur at the burning surface but, the chemical reactions of combustion/burning process; not at all.

From what I have read your source is correct if you are talking about NC while it is in the wet stage of the manfacturing process. My understanding of it is, it’s at this stage where the manfactures set the viscosity parameters (mean molecular mass). Kiering / boiling or steaming with water and or slightly alkaline water lowers viscosity and reduces nitrogen content through hydrolysis. The percentage of nitrogen content in NC affects the mechanical properties, energy content, linear burning rate coefficient, and pressure exponent.


Ken
 
HBC said:
K Hope,

".... and the loss of energy to latent heat of vaporization and likely energy lost in dissociation of the hydrogen and oxygen molecules at high temperatures as the powder burned...."

Henry
Click to expand...

It is very unlikely that the temperature of a chamber (<3,000 F) could break the hydrogen-Oxygen bond - as even in a Oxy-hydrogen torch, the two atoms combine, not break apart, and that is in the ~5,000 F range.
 
In your first post of 7/15/2011, I am not following the reasoning. My test is about adding water to finished dry charges of smokeless powder and comparing the performance to finished dry smokeless powder of the same charge. My test is not about “NC while it is in the wet stage of the manufacturing process.”

My first post was an outline of the test. My second post was quotations from Sharpe’s book about the manufacture of smokeless powder to give shooters the benefit of the information on manufacture of smokeless powder in Sharpe‘s book, a book I purchased in 1958. In those quotes he described the process starting with cotton linters which continued through the green powder stage and finishing with completed, dry and blended smokeless powder, smokeless powder ready to use.

In your second post of 7/15/2011 it is stated that the chamber temperature in rifles is less than 3000 F. I do not believe that is the case but if you have evidence to support the statement, I truly would love to see that evidence, read, enjoy and learn from that evidence.

Note in the data I posted from the AIAA reference, giving an isochoric temperature of 4643 F for an IMR powder. That is for a test in a closed chamber with the smokeless powder gases doing no work. In a rifle barrel, the propellant gases do work, moving the bullet and giving kinetic energy to the bullet and to the gases themselves, thus the propellant gas temperature in a firing rifle would be less than the isochoric temperature for the same powder, determined in a closed bomb calorimeter.

I have read that hydrogen is a byproduct in steel mills, resulting in water splitting of the quench water used to cool hot steel (steel that would be below a temperature of 3000 F). In addition, Wikipedia gives the temperatures required to split water in the range of 1472 F to 2192 F.

Henry
 
First, I gave 3,000 as an upper limit. While it is not realistic to measure the actual temperature inside a chamber, it can be approximated by the damage the heated gases do, and I think 3,000 as an upper limit is a reasonable estimate.

As to oxygen and hydrogen in steel mills... that reaction is a "reduction reaction" where the oxygen is taken by a "hungrier" atom, leaving hydrogen behind - a similar reaction is when you put sodium in water - the sodium takes all the oxygen and some of the hydrogen, and leaves gaseous hydrogen behind (which catches on fire).

As to water breaking apart into oxygen and hydrogen at 1,472 degrees. It is just not possible. If it were, then raw oxygen and hydrogen would be released in huge volumes at the sites of underwater lava flows in Hawaii, but it is not present.

Also, since the oxy-hydrogen torch reaches ~5,000 degrees, you have a situation where, IF water would disassociate at 1,472 degrees, then the hot water vapor formed by the oxy-hydrogen flame in the torch, would then break apart into oxygen and hydrogen, but now being a flammable combination of gases, would burn and form heat, which would cause them to break apart, but now being a flammable combination of gases, would burn and form heat, which would cause them to break apart, but now being a flammable combination of gases, would burn and form heat, which would cause them to break apart...

And by now, you should recognize the (in)famous "perpetual motion" machine, which (of course) can not exist, nor does water break apart with the application of heat until the temperatures reach astronomical levels that are way above what we are dealing with in a chamber.

And none of this crap belongs in a shooting forum.
 
I and many others were sortof enjoying it being in a shooting forum.

Your perpetual motion analogy ignores all other losses of energy as well as the expansion of the gases into the surrounding atmosphere. I'm no chemist, so I'm not going to debate the subtleties of this. But if you'd like to expand upon the statements above, I know I for one will read with interest. I've not followed this thread all that closely. I did read the parts that were written here. (not all the stuff Henry quoted for ref). I'm gonna bet though that if you can convince him there's an error in the works somewhere, he'll re-order all the findings accordingly.


/edit
Just to add my personal opinion (which is of course not up for debate). If you do not think this subject belongs in a competitive shooting forum, then you do not belong in a competitive shooting forum.
 
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HBC said:
K Hope,

I have been told by a reliable source that at least one smokeless powder manufacturer adds water to lots of powder in order to reduce the burning rate.

Henry
Click to expand...

The Reasoning:

Water is added to industrial nitrocellulose in order to reduce the flammability and burning speed but I have never heard of the manufacturers of smokeless powders adding this variable to set standards.

As I see it the water content has more to do with arriving at a set energy content and adsorbed water has more to do with changes from that value.

Through comprehensive controls, before, during and after the production process manufacturers are able to achieve a controlled specific standard required to establish a set energy content with the least amount of variations. (e.g. Burn Rates)


Not looking for anything other than the understanding of the process and looking forward to your follow-up data.

Ken
 
K Hope said:
The Reasoning:

Water is added to industrial nitrocellulose in order to reduce the flammability and burning speed but I have never heard of the manufacturers of smokeless powders adding this variable to set standards.

As I see it the water content has more to do with arriving at a set energy content and adsorbed water has more to do with changes from that value.

Through comprehensive controls, before, during and after the production process manufacturers are able to achieve a controlled specific standard required to establish a set energy content with the least amount of variations. (e.g. Burn Rates)


Not looking for anything other than the understanding of the process and looking forward to your follow-up data.

Ken
Click to expand...

If you want reasoning, consider this - you make gun power that is used by amateurs with no scientific equipment, to load cartridges - they use loading manuals with the amounts based on tests, and they push their loads to the max + 10%... especially those goofie bench rest shooters that load to ~70,000 kpsia.
They test their loads, and come to some sort of load and count on the powder to be consistent for the rest of the 8 pound jug.
They cannot re-test the load every time they go to shoot.

Now your head chemist has come up with a brilliant thought... "Hey Boss. I can save us some money. Instead of using burn rate deterrents and grain sizes to control our powder burning rates, we can use water!"... long silence in the board room, then the Boss says...

.... "Are you out of your God-damned mind???"

See, the lawyer (which all powder companies have (by the dozens) says, "How do you control the water after it leaves the plant - a re-loader leaves the powder in his measure, cuz his kid got hurt in school and he has to rush to the school, and gets home three hours later, and he lives in Arizona, where the humidity is -20, and continues to load the same load... so now the rest of his loads are not 65,500 kpsia, they are 77,900 kpsia?"

The point is that NO responsible manufacture of powder would use water to control burning speed - that is not how powder is made, and it is not how burning rates are determined or controlled.
 
4Mesh said:
/edit
Just to add my personal opinion (which is of course not up for debate). If you do not think this subject belongs in a competitive shooting forum, then you do not belong in a competitive shooting forum.
Click to expand...


You are right - I don't belong here.
 
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