Smokeless powder moisture content. Something else to consider

[TXSGFmrCWO3]

I just ran across this on thefirearmblog.com, referring to an article by Vihtavuori.

"Comparing results showed chamber pressures increased from 320 MPa to 355 MPa with the dried powder, and the muzzle velocity increased accordingly from 770 m/s to 790 m/s (2526 to 2592 fps). And note, this is only one example, of one caliber and loading. The difference might be much higher depending on the cartridge and loading combinations."

Perhaps this might explain some of the headscratching, sudden increases in velocity that can't be attributed to temperature?

https://www.thefirearmblog.com/blog/2018/07/23/wisdom-from-vihtavuori-powder-moisture-content/

 

[mdmp5]

Yes. This is important when you leave powder in the hopper for a while. I’ve been guilty of leaving powder in my chargemaster for a few weeks. I don’t remember correlating the fliers to that, but it may have contributed. I think to be sure from now on, use whatever powder you’re gonna use and put the rest back in the jug

 

[TXSGFmrCWO3]

Yes. This is important when you leave powder in the hopper for a while. I’ve been guilty of leaving powder in my chargemaster for a few weeks. I don’t remember correlating the fliers to that, but it may have contributed. I think to be sure from now on, use whatever powder you’re gonna use and put the rest back in the jug

Great point. Luckily, I started reloading in the dinosaur days when powder hoppers would score or melt if you left the powder in them to long, so I always empty as soon as I'm done for the day.

I wonder if there's a convenient way to check the moisture content?

 

[mdmp5]

Convenient, likely none, especially at the levels of hydration we are talking about. I think the only way to truly measure would be to evaporate the moisture and take a before and after weight.

 

[Precision Underground]

I’ve always wondered why silica packs or something aren’t used to keep moisture out. Anyone?

 

[mdmp5]

I’ve always wondered why silica packs or something aren’t used to keep moisture out. Anyone?

It’s not about keeping moisture out, rather keeping it consistent.

 

[Precision Underground]

It’s not about keeping moisture out, rather keeping it consistent.

That makes sense. I didn’t realize there was any moisture in it but I guess there always has to be some level of it.

 

[mdmp5]

That makes sense. I didn’t realize there was any moisture in it but I guess there always has to be some level of it.

Yeah the ideal storage conditions are cool with average humidity

 

[Fatelvis]

Considering this variable, would it be a better Idea to purchase 8 separate 1# cans of powder of the same lot, or one 8# jug, if one was to load for a cartridge over about a year? Idea being, that only one pound is used at a time, as the others are left sealed, keeping the original humidity level. Your thoughts?

 

[TXSGFmrCWO3]

Good point. As long as they're sealed, contents have a long shelf life. Perhaps quantities of 1# containers is a better idea for lower volume reloaders.

 

[Bradu]

Yeah the ideal storage conditions are cool with average humidity

That's part of the reason why my house is heated or cooled year round, allergies is the other reason.

 

[Precision Underground]

That's part of the reason why my house is heated or cooled year round, allergies is the other reason.

I was wondering that. Would leaving powder in the hopper not be that bad if it is always climate controlled? And I keep my AC on about 68 lol.

 

[spife7980]

Wouldn’t that still be a different humidity level than the powder though? Just don’t leave the jug sitting open and you’ll be fine

 

[TXSGFmrCWO3]

Powder hoppers are typically not "sealed." At least my RCBS uniflow isn't.

Humidity can vary greatly in a climate controlled environment. Best to verify with a hygrometer.

 

[davethedog]

Not to dig up an old thread, but here is some data about that. Blue points are from fresh powder, red points are from just a few days in my autotrickler hopper. I live in Colorado and it’s winter here, very low humidity dries this powder out pretty quickly evidently.

This is 8133 in a 300 PRC.

 

[Zatchmo]

Another data point. "Sealed" containers aren't exactly sealed either. Also in Colorado, but in a climate controlled (humidity included) house. In the basement, so a little more temperature fluctuation. This was a fresh 8 pounder of H4895, opened only to drop the wireless sensor in and then sealed back up. 5 ish weeks of data here so far.