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Bolt action reloading did a interesting test with dramatic results. Check it out. https://www.youtube.com/watch?v=pzDHRwi3QVk
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Interesting, and shows a wide variation in powder performance for humidity levels... same quantities of powder with varying levels of water present (thus, same amount of burn energy available, just distributed differently due to dealing with the water).
But when you think of it, this is understandable due to the water content present (or not) within the powder itself. The water carried inside would do 2 things:
1. Reduce available heat energy for combustion by taking some amount of energy for its own vaporization
2. Reduce the burn rate of the flame by lowering its temperature - again due to water presence doing some amount of cooling
Water's heat of vaporization is substantial, so I think it would be understandable that the increased humidity would have a larger effect than the dry condition, relative to the mid-level humidity.
This speaks more about the need to have your reloading room in a temperature and humidity controlled room (ie, heated/AC) where indoor humidity is (relatively) constant, as opposed to in a garage or unheated space... but even at that, in winter time I'd guess indoor humidities are lower than in AC-cooled summer conditions even inside (my reloading rooms have been indoors for most of my reloading life). Going from a mid-level (summer/AC) of say, 40%, to a winter level of, say, 20%... some amount of delta but not sure it would be as dramatic as in the video."Down the floor, out the door, Go Brandon Go!!!!!" -
In this Everyday Sniper podcast, Bryan Litz talks about the same issue. That video and the podcast started me thinking about the issue.
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WOW! That does help explain some mysteries. I used to blame variable velocity data on the low quality sky-screen chrono I had been using, but that didn't completely go away when I switched to LabRadar. This makes much more sense.
This is part of the reason I load in bulk, vs just loading 100 rounds here, 100 there. But what's eye-opening is that bulk-loading tends to follow the test-load development work by weeks, if not longer - which can be very different humidity conditions.
I'm going to order one of those data-logging phone-syncing hydrometer rigs. You can get one for like $12, so why not...4x P100Comment
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Can you post a link to the "data-logging phone-syncing hydrometer rigs." please.Comment
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4x P100Comment
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I'm trying to quantify the effect. I agree there is some, but form what I heard on there, their testing went from 2% to ~80%, those 2 data points. So effectively a 1-1.5 gr swing of the medium powders = 60-90 ft/s in MV (creedmoor/308 powders). Also if I heard/read correctly someone logged a 100 ft/s change, again with a large swing in humidity.
I do all my reloading in a Heated/A/C environment (indoors) with temp controlled ~72, humidity doesn't vary by much, maybe 20% from summer to winter. So any effects I should expect to see would be ~20 ft/s, maybe?
Also, regarding humidity creeping into loaded cartridges, true neither the bullet nor the primer is a hermetically sealed component, but I doubt seriously if there is much moisture transfer across either boundary. To do so would imply gas/mass transfer across that boundary in order to accomplish that, yet the cartridge is typically iso-thermal to the surrounding environment (so what's the driving force for the transfer? nothing I can see). Now this all is with respect to my loading conditions, in which temp and humidity don't vary by the large swings in the articles.
Or am I missing something..."Down the floor, out the door, Go Brandon Go!!!!!"Comment
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At 9:30 into the BoltactionReloading video he got an average 220 fps difference. Three data points, High, low and room humidity.
I'll just avoid loading ammo during rainstorms or monsoon type weather and keep my powder away from the bathroom.
I can't recall who but there was a vid of someone's mea culpa how he didn't dry out the brass very well after wet tumbling and when loaded it messed up the batch.
It would be helpful if reloading sites and books would publish what the humidity was when they generated their data.Comment
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Water content in powder will also add weight to the charge, reducing the powder weightComment
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I think the main message is what you're saying here, avoid high (and low I guess but that's not as much a worry imo) humidity - lowers the burn rate and lowers the actual powder weight. If we keep powder at a relatively controlled T/H then the only real variable outside becomes, like before, temperature in the field and powder sensitivity.Originally posted by Lemonaid View Post
It is nice to have some data points on it, however.
The actual powder pressure/temperature (under normal circumstances) of the powder, speed of the powder burn and case size (amount to burn) also probably figure in to how much MV loss a round might see, compared to its nominal environment-load. Smaller cases like Grendel might suffer relatively more loss than a larger, 308 or Creed case... maybe."Down the floor, out the door, Go Brandon Go!!!!!"Comment
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Lucky for me I live on the Gulf Coast so the humidity is constant... Have you ever noticed that when you drop a powder charge on the scale and leave it sitting it gains weight. That is result of it absorbing moisture out of air. My powders and primers are stored inside house in AC ... same goes with my dies, reloading bench, and anything else I want to stay rust free.
My brother just dropped off a Ruger Mark 1 that he shot at range 1 weeks ago. I opened up the soft gun pouch to find a nice pistol with barrel covered in surface rust pattern matching 4 fingers wrapped around it. All bare metal, including blued steel, immediately gets wiped down with oil after use. All new rifles are either stainless or cerakote finish... no more bad dreams of rust in the safe. If Howa Mini shoots well then it will get a cerakote finish, and if it shoots poorly it will get a new barrel and then a cerakote finish.Comment
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Thanks, looks like it could be interesting, but I do have a Kestrel Drop. cost more than 12.00 though, but I was able to get it with points.Originally posted by lazyengineer View PostComment
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Here is where things could get dicey. Suppose you live in a mostly constant high humidity area like by the coast in Texas and make up some loads .5 to 1 grain shy of maximum safe pressure. They work fine in your area and are safe. Then you go to a hog hunt in a dry climate and have your ammo in the car trunk that gets fairly hot for a few day as you travel. Is the ammo still safe?
Sounds like that would be an interesting experiment to do but to be safe back off 4 grains shy of max and see what the velocity difference is.
Anyone have a good idea of how long it takes loaded ammo to change it's humidity when in a hot car?Comment
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Lemonaid- in that scenario it sounds like a metal/plastic ammo can with a rubber gasket would be wise if you were worried about it.
Here is SC we live with high humidity daily. Currently 99% at 6:45 am. I do load in a-climate controlled environment with just enough powder out for the current tray of brassComment
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"Anyone have a good idea of how long it takes loaded ammo to change it's humidity when in a hot car?"
No, I don't, and I have way too many other things to do besides taking the time and components to try to find out.
Temperature differences with temp sensitive propellants would probably be of greater importance to me. It might be a great way to
kill some time for these with a lot of time on their hands, but how would one set up the necessary conditional controls and then apply the results. Some interesting theoretical concepts, but what to do with them?Comment
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