Humidity and its effect on black powder

Hi guys,

I am back to shooting black powder consistently after a break of several years. Being retired I can squeeze in 4 practices and 2 different club shoots a month.

What has become apparent to me is the difference upon black powder fouling between winter and summer humidities. I live in the tropics just above the Tropic of Capricorn..

In the winter we have just had, I could shoot 20 shots and not suffer much from powder fouling. Just lately our summer is just starting and the humidity is climbing.

The powder residue is now turning tarry and I find I need to swab out after 1/2 doz shots or so.

Nothing at all in the load chain has changed since summer.

Using German Wano FFG , .535 ball, .012 patch in a .54 Pedersoli Tryon. No blown patches or patch cutting. Clean/swabbing with a mix of equal amount clean green, Ballistol, and water. The gun still shoots well enough for me to pick up some events in a recent Rondy, but I still would like to sort out the fouling if it is at all possible.

In other words the only variable is the humidity level.

Seeking your experiences, observations and hopefully a cure.

Thanks in advance

Whitesmoke.

Humidity does effect loads as well as allot of other factors of coarse.

* RH below 40% and high ambient temperature = hard bore foul
* RH above 40% and low ambient temperature = soft bore foul
Black powder is hygroscopic and the more moisture drawn in from the air, the softer the foul
https://en.wikipedia.org/wiki/Hygroscopy

Given the variations in humidity I don't believe there is a cure. We have a similar situation where I live and if it's one of those foggy, high humidity, moderate temperature days the fouling in the pan of a flintlock can get so soupy it will foul the priming charge if it isn't wiped out.

I believe that the serious BPCR competition shooters will tell you that more humidity is better, for the reason stated above; the fouling is softer with humidity. That's why there is such a thing as a "blow tube". In revolver shooting, I always "blow down" the gun after finishing off a cylinder full, and I can feel the gun loosen up right away as I start blowing on it.

And so it is that BPCR shooters have also told me that they're more likely to use a "lube cookie" behind the bullet in very dry weather, whereas in wetter weather they may rely only on the lube carried in the bullet's grease grooves.

Your other variable would be temperature, I assume, and I don't know the effects on fouling in colder verses warmer weather, as I always use a lube cookie anymore and thus, combined with blowing the gun down after every six, I don't have fouling problems. Ever.

And to be clear; it isn't the powder's hydroscopic nature we're discussing, but the powder fouling, which is something different. I don't believe the powder itself is hydroscopic enough to be much of an issue. I've shot in the rain (percussion system) and not had any trouble.

Anyway, the term “relative” humidity may be a problem here in our assumptions, as in very, very cold weather for example there is an extremely small amount of moisture in the air, and yet the “relative” humidity may be very high. In that case, a warm barrel, with outside air inside it, will be extremely dry no matter how you look at it. So when we’re assigning RH thresholds to the situation, we’d have to specify a temperature range, and even then it’s coming down more to the temperature inside the barrel at a given moment.

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Really you can forget all that stuff though. If bore fouling is becoming a problem it means you’re not using enough lube, the “right amount of lube” being defined as that amount which results in no fouling problems for a given load and environmental situation.

I choose to look it like that, and so far it’s been working, and so I don’t have to care about the science and physics of the situation beyond what I can see and feel in the gun right there on the spot.

It really isn't rocket science. Well OK, it IS rocket science, but it is very basic rocket science. More like "rocket art".