I would suspect that is something other than humidity. It doesn’t change that much in an enclosed space that fast just because the a/c cycled off.

Some guys are on the quest of very precise, very consistent ammunition, specifically made for their rifles.

Why throw rocks at them?

Continuing to improve is the opposite of living in a rut. And the worst rut is the "way we've always done it" rut.

You are right of course, but sometimes the minutiae and esoterica become overwhelming to the point of paralysis, and we reach diminishing returns. A paradigm shift provides a simpler, more useful solution. For example, it’s now easier to kill something at a mile with a cheap drone than with an expensive rifle. Things change.

Ive already been down that path decades ago. I live close enough to the coast to get the full influence of the gulf humidity. Weeks with a 70% swing in humidity happen here. In spite of the humidity swings the ammo I handload
Is more consistent and precise than the Hornady ammunition that was touted earlier in this thread. Humidity makes more difference in bullet flight than powder charge influenced by humidity per my experience. Humid air will cause impact to slightly rise. Dry air will cause a lower impact. Even that is so minuscule that at 800 yards it is less than the incremental adjustments on my turrets in the 7-08 and 7RM that I shoot longer targets with. Air flow from an indoor central air unit also causes more variation in powder charge than humidity per my experience. I wasn’t throwing rocks. I was sharing what I’ve found rather than read on the internet.

Go back to the first page. You will see where I mentioned ammo loaded in a non-HVAC environment, and loaded on different days was not competitive in a rifle match. Environmental changes to bullet flight have much more effect than the humidity trapped inside the powder. But humidity variation in the powder AND environmental changes do add together. And can cause misses depending on what a guy is trying to do.

Loading in batches is proven.

its a wonder that hunters in the early days brought home any meat.

Those hunters were satisfied with ammo that stayed inside deer vitals at 100 yards.

Today we have the knowledge, and equipment to stay inside of squirrel heart at 100 yards. Might as well take advantage of that knowledge and equipment.

I didn’t forget.

This RL19. One sample inside climate control, one outside with cap slightly loose to absorb moisture.

The RCBS Matchmaster shows a +/- .04 grain consistency, so showing .04 difference is within the accuracy of the scale. Meaning, there is no difference from 100.0 to 100.04 with that scale. If the difference were larger, say .08 or 1.2, then it would be a measurable difference with that scale.

Well that wasn’t the in and out test. That was the measurement of the samples before the test.

For the record the heavy one is outside.

Redundancy

It "gained" .04 gr of weight.

You weighed both batches 100.00 gr, then sat one batch outside.

No sir, two different samples. I’m waiting on their measurements

Wow, looks like a buncho bitches.

I'm looking forward to your results.

Significant findings this morning.

Inside




Outside




It appears the outside powder that was kept dry but exposed to humidity gained .20 grains. Is this enough to be relevant? Probably not at my house.

.2 gr on a 100 gr load no.

.2 gr on a 24.0 gr load, maybe

I test .223 Rem in .2 gr steps.

I am curious. Does the 0.2 grain increase actually change anything if we do not know how the absorption of moisture actually affects the ignition properties within the case? Does the 0.2 grain increase change the internal fill capacity of the case or is this just merely a cosmetic weight increase. Is 0.2 grain of moisture absorption truly equal to adding 0.2 grain of actual powder? I am suspecting this is not the case since water is much more dense than one stick of extruded powder.

I would like to see this test performed with some sort of graduated glassware so that we would be able to see the volume differences to ascertain whether or not there is a physical change to the internal fill of the case.

I am a laboratory manager by trade so these things always get the analytical side of my brain going into overdrive.

I don’t think there is a measurable change in volume. The only downfall I see is if you load on days with significantly different humidities your load will be off. I don’t consider .2% to be enough to worry about. The average case I load with 40.0g of powder. That .2% is equal to .08g. Also, this testing was done in extremes. 99% humidity outside and relatively low humidity inside. I didn’t have a means to check it but I turned the heat up so it wouldn’t cycle off much.

There is a reason the short range BR guys load at the range.

When I was shooting longer range BR...rarely did I not load the night before a match....but our matches were not high volume like that PRS guys, a match for us is 50-55 rounds.

For a PRS style match, where you're going to exceed 1000 yards, it is wise to load your 300 rounds in the same sitting. And only a day or two before the match.

Learned the hard way.

... why only a day or two before the match?