Pyrodex shelf life information

[Mad Monk]

Paul,

To expand a bit on what you are saying.

The time of year has a lot to do with how the powder reacts to any air around it in a container. This would be in working with partial cans of powder or flasks or horns that are not full.

When you fill a measure from a can, horn or flask you allow air in each time you pour powder from one.

Relative humidity percentages are only part of the story.

At 40 F with 100% R.H. a cubic foot of air contains 2.861 grains of water.

At 90 F with 100% R.H. that same cubic foot of air contains 14.96 grains of water. That is 5 times more moisture than at 40 F.

A local bp writer got into this with me one summer. He had been asked to test some bp by the manufacturer. He was doing the shooting in August on a day that was hot and very humid. Shooting over a chronograph.
As he was shooting his velocities began to get a bit lower with each string of shots. By the time the can was almost empty the drop in velocity was rather noticeable in the chronograph data.

With BP you usually see powder from a fresh can have a moisture content of around 0.4 to 0.5%.
If the powder begins to pick up moisture you don't see much of a velocity depression effect until the powder moisture content hits around 1%. Increase the moisture content of the powder over 1% and the velocity depression then becomes rather noticeable in the chronograph data.

I have gone over this with the powder producers relative to their respective sources for potassium nitrate. No sodium nitrate in with the potassium nitrate is critical. Even small amounts of sodium nitrate in the potassium nitrate will yield a finished powder with a very great affinity for moisture in the air. Properly prepared black powder is almost non-hygroscopic.

And this thing about being almost non-hygroscopic is where the subs fall flat on their faces!

 

[paulvallandigham]

MM: Thank you for that follow up. I learn more and more with every post you write. Thank you for sharing all your expertise. Your knowledge of chemistry is awesome.

I have had the same experience with BP and moisture varying depending on what time of the year I am shooting. I used to host a " Bull Shoot " on January 1, every year at my club, simply because it would usually be below freezing all day long- often below Zero! - and the guys would have to learn how to change their loading procedures used in the summer in order to load and clean their guns in the much dryer air, and in the freezing temperatures. The first time I proposed such a shoot, the officers thought I was nuts. No one shot their ML rifles in freezing temperatures. I reminded them of all our brothers and friends who live in Canada or Alaska, and shoot all year round. If they can fire their guns in those temperatures, we certainly can learn to do the same here. I was the only member who shot a gun on that first Bull Shoot. I used rubbing alcohol to wet patches and to clean the barrel between shot. My fingers got cold from the evaporating alcohol, but it got the job done!

The next year we had 6 shooters, and after that, it became one of the most popular shoots at the club.

I obviously don't know or understand very much all the intricacies of the chemistry of the new subs. I am a lawyer, not a chemist. There is a limit to what you can get into my thick head. But, after reading all I can find about them, it seems that you have to treat them like you would smokeless powders finding a cool, Dry place to store them, and then try to use up your can of powder within a couple of years if it has been opened from any appreciable time in high humidity conditions. My father loaded in a room in the basement, opposite the laundry, but when mom was washing or drying clothes, he would stop loading. The basement was a steambath even in the winter, when she had that dryer going, even with the outside vent.

 

[Mad Monk]

Paul,

Re shooting bp in cold weather.

BP's ability to burn at very low temperatures is one of the reasons that it still sees use in military applications. Smokeless are difficult to ignite at low temperatures and then slow to pick up their burn rates in extreme cold. The use of bp as an intermediate igniter helps to overcome the low temperature problem with smokeless.

 

[jtmattison]

I am a lawyer, not a chemist.

Here come the lawyer jokes :haha:

HD

 

[jtmattison]

Mad Monk,
Thank you for all of the input.
Thanks to everyone.
This has become a very informative thread.
:hatsoff:

HD

 

[paulvallandigham]

I resemble that remark!!! :thumbsup: :rotf: :rotf: :rotf:

 

[Mad Monk]

Paul,

Don't let them bust your chops about being a lawyer. There are a fair number of good ones around. I do WC case law research for one here in town. He does not do criminal cases. Sticks with WC and does a lot of stuff for the office of aging where he does not get a lot of money to do it. A real stand up guy. He helped me out in the past so I do the case law research work and accept no money from him.

Now there is one who runs at the sight of me.