Humidity and load developement

degreen

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Anyone test the effects of humidity changes in the reloading room while doing load development? Just watched a video on YouTube about how high and low humidity levels effect load development.
 

BFD Guns

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Nope, I would think the changes in baro and temp would far negate the humidity on the powder at the time of loading. However, there might come dissenting opinions.
 

Pdyson

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I haven’t but Michael Coppola did. In the not so distant past I have inadvertently left powder in my powder measure open to the air for weeks. 22% humidity change can affect velocity by 55fps. I thought it ok if I kept the bottle it came from next to the hopper. Started doing that to keep from dumping powder I could not remember what it was when I pored it. I bought a dehumidifier and a AC unit to keep my reloading area around 50-60%. If it’s really high, I won’t crack open a bottle. Here is a link to the test on H4350.
 

BFD Guns

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I haven’t but Michael Coppola did. In the not so distant past I have inadvertently left powder in my powder measure open to the air for weeks. 22% humidity change can affect velocity by 55fps. I thought it ok if I kept the bottle it came from next to the hopper. Started doing that to keep from dumping powder I could not remember what it was when I pored it. I bought a dehumidifier and a AC unit to keep my reloading area around 50-60%. If it’s really high, I won’t crack open a bottle. Here is a link to the test on H4350.
Last time I ever try talkin out my arse!
 

degreen

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I haven’t but Michael Coppola did. In the not so distant past I have inadvertently left powder in my powder measure open to the air for weeks. 22% humidity change can affect velocity by 55fps. I thought it ok if I kept the bottle it came from next to the hopper. Started doing that to keep from dumping powder I could not remember what it was when I pored it. I bought a dehumidifier and a AC unit to keep my reloading area around 50-60%. If it’s really high, I won’t crack open a bottle. Here is a link to the test on H4350.
In the video I watched. The guy showed velocities between rounds loaded at 90%, 38%, and 10% humidity. There was a 200 fps difference between the 10% and 90%. With the higher velocity going to the 10%. Makes me rethink my load development, and wonder just how many times I was chasing my tail due to humidity.
 

Barrelnut

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I really try not to leave powder in the hopper overnight. Because of the exact tests mentioned by Pdyson above. I said try....
I live in an area though we're the average humidity is about 50% year round. So I don't freak out if I happen to leave it there for a couple days.
I keep a "cheap" Therm Pro temp and humidity gauge above my bench. It keeps track of the highs and lows.
In the last 3 months:
Humidity has fluctuated from 42% to 68%
Temp has fluctuated from 61 degrees to 76 degrees
Currently:
Temp: 68.2 degrees
Humidity: 56%
 

BFD Guns

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I load in the winter. I load in the summer. I live in IL where summers see 100% humidity. My room is in the basement with more atmospherically controlled temps, but I'm sure there is a range of humidity inside my house by 40%. I shoot these rounds few times a year and they fly where I expect depending upon the temp. In 20yrs I haven't even thought about this topic you are worried about because I have not seen any appreciable difference. Though I'll admit I've never looked for it. The internet can provide solutions to problems that don't exist.
 

Barrelnut

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I load in the winter. I load in the summer. I live in IL where summers see 100% humidity. My room is in the basement with more atmospherically controlled temps, but I'm sure there is a range of humidity inside my house by 40%. I shoot these rounds few times a year and they fly where I expect depending upon the temp. In 20yrs I haven't even thought about this topic you are worried about because I have not seen any appreciable difference. Though I'll admit I've never looked for it. The internet can provide solutions to problems that don't exist.
Believe the question has to do with humidity in the reloading room and leaving the powder exposed in that reloading room for an extended period of time. Powder will absorb moisture in a humid environment like Florida and loose it a very dry environment like Arizona. This changes the weight of the powder and since we load by weight it can affect the velocity. Drier powder ends up having a faster burn rate and vise versa.
 

Reelamin

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Oh lordy lordy....now the internet wizards are putting out we need to keep the atmospheric conditions the same while reloading? Funny to me how things are changing and yet are not changing. I'm old and have been around serious (go around the country shooting serious) BR guys since the late 70's AND HAVE NEVER EVER HEARD THAT YET!!
 

Muddyboots

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First I never leave powder in hopper after I had to toss it once because I did not label it and I had loaded several cartridges and could not recall the exact order of loading the cartridges few days later. All extruded so no chance at guess. Of course now I place a post it on hopper as old geezer reminder. I load in basement in MI and doubt the humidity changes much especially in winter with hot air heating. I also use a small container to transfer powder to weigh pan while the powder container is tightly sealed. Hardly any exposure time. Have to refill several times to load 20 rounds but time is not an issue when retired! Guess I was addressing humidity concern without even knowing it!
 

Jud96

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Humidity definitely affects velocity. I never thought about it because I left my powder in the original containers and in a house with AC that stayed relatively the same temperature and humidity year long. Fast forward, I moved to Michigan last Fall. I noticed after several months something odd was happening. All of my velocities dropped 20-30fps in multiple rifles with the same load, same components, same lot, broke in barrels etc etc. The only change was moving to Michigan, which has higher humidity than West Virginia, and the fact my home in Michigan currently doesn’t have central AC. I kept all of my powder in a spare closet and the room wasn’t temperature or humidity controlled. I didn’t even think about it since the powder was in the original containers and never gets left outside of the jugs. I’m going to experiment with some cigar humidor packs in the powder kegs and see if keeping the powder at one stable humidity level keeps things more controlled and consistent. I have a dehumidifier in my basement by my reloading bench and may store the powder there because the humidity is controlled and my basement is leak free.
 

degreen

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Oh lordy lordy....now the internet wizards are putting out we need to keep the atmospheric conditions the same while reloading? Funny to me how things are changing and yet are not changing. I'm old and have been around serious (go around the country shooting serious) BR guys since the late 70's AND HAVE NEVER EVER HEARD THAT YET!!
There is a huge difference between benchrest and hunting. You don't get sighters when hunting so that first shot has to count. If the humidity of the powder effects velocity, and velocity effects harmonics then that quarter MOA group could now be a three MOA group.
 

Old rooster

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When I reloaded in Louisiana I was in 90% to 100% humidity and loaded a 30-06 180 gr Partition at 56.4 gr of IMR4350 and got great results but here in Montana we have very low humidity and when I tried to load at 56.4 gr I got a heavy bolt lift and now I know why.
Similar results with Hornady bullets too.Now I know the reason
 

Deputy819

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Anyone test the effects of humidity changes in the reloading room while doing load development?
Inadvertently. Left some RL 26 in the hopper of the Chargemaster for @ a week after developing a great load for my .300 Win Mag using the Berger 210 vld’s. Loaded up some afterwards and my “great load” had gone to the proverbial “crapper”. Not understanding why I shot a few over the Magnetospeed and it indicated a 40 “ish” FPS decrease in velocity which had taken me out of my node. Never made that mistake again. 😐
 
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