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Powder moisture and velocity?

RabbitSlayer

A couple months ago I tested a 223, 25.5 gr of TAC, with 53 gr vmax, and for 25 shots the average was 3293 at 97 degrees. I then loaded a couple hundred.

Last weekend I shot 50 of them and the average was 3360 at 65 degrees. I was expecting slower not faster! I had opened a fresh 8lb jug. It was a couple weeks after initial testing till loading the rest. The loaded rounds sat maybe 4 weeks. I live in las vegas, so the humidity is crazy low. Can the powder drying out really change the velocity that much? I did not let it sit in the hopper between loading sessions.

My other theory is neck weld? I graphite lubed before the mandrel, but not before seating. Its new brass
 
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powder has a moisture content yes my brother use to dry 7828 for his 300 MP to gain 175 fps all I knew is he dried it, he said he did and the Chrono proved it, I think he used some sort of strips and weight volume to verify.. it will gain burn speed as it gets dry
 
RabbitSlayer said:
A couple months ago I tested a 223, 25.5 gr of TAC, with 53 gr vmax, and for 25 shots the average was 2293 at 97 degrees. I then loaded a couple hundred.

Last weekend I shot 50 of them and the average was 3360 at 65 degrees. I was expecting slower not faster! I had opened a fresh 8lb jug. It was a couple weeks after initial testing till loading the rest. The loaded rounds sat maybe 4 weeks. I live in las vegas, so the humidity is crazy low. Can the powder drying out really change the velocity that much? I did not let it sit in the hopper between loading sessions.

My other theory is neck weld? I graphite lubed before the mandrel, but not before seating. Its new brass
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I shot an f-class match a few years back with 6BR ammo that I had loaded 13 months prior that sat in my safe and only dropped 3 points in all 3 relays. Over a year and no neck welding so I would doubt you would see it in a few months of being stored.
 
Capt. Oblivious said:
Dryer powder does shoot faster but powder in loaded ammo (essentially a sealed container) cant dry out like that.
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I've wondered a bit about this... we all assume that once loaded, the cartridge is essentially a sealed container, with no moisture exchange in or out. But... one has to wonder, if that's so, why do militaries bother sealing their ammo? Granted, those rounds are likely exposed to far worse conditions, and probably over a much longer time, than anything we're realistically concerned about here.

My thought/concern was when transporting ammo over a long distance, to a very different environment. Say going from nearly sea level, with a relatively high humidity, to some place at a fairly high elevation, with low humidity e.g. Raton NM. Could the change in atmospheric pressure act to increase the likelihood of moisture exchange in some small sub-set of rounds being transported to a match. Or... if one is having ammo shipped ahead to an event via air, or transporting it via checked luggage in an environment very different than that in the main passenger cabin... could that act to weaken whatever 'seal' exists along the interface between the bullet and the case neck, or the primer and the pocket, and allow some moisture exchange? Would it even be enough to matter?

Probably getting a little far afield from the original post, but figured I'd throw it out there anyway ;)
 
It always seemed when I shot at something in the mountains I missed it high.. If I missed which was very likely. I hadnt been out there long enough for my powder to dry out. I thought it was moist air dry air thing. Sight in Mo. and travel up for 2 days and go hunting. Doug
 
Doug Casner said:
It always seemed when I shot at something in the mountains I missed it high.. If I missed which was very likely. I hadnt been out there long enough for my powder to dry out. I thought it was moist air dry air thing. Sight in Mo. and travel up for 2 days and go hunting. Doug
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I don't think that is the cause.
Atmospheric conditions are what changes. Ballistic calculators can help you in the right direction on this.
 
It sounds like the rounds were loaded from seperate containers from the description. If so its likely Lot differences.
 
Doug Casner said:
It always seemed when I shot at something in the mountains I missed it high.. If I missed which was very likely. I hadnt been out there long enough for my powder to dry out. I thought it was moist air dry air thing. Sight in Mo. and travel up for 2 days and go hunting. Doug
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6.5 forever said:
I don't think that is the cause.
Atmospheric conditions are what changes. Ballistic calculators can help you in the right direction on this.
Click to expand...
I agree. That is likely barometric pressure which decreases with altitude or a combination of atmospheric conditions.
 
Think about the load as two separate components. There is powder, and some water in the powder. The powder starts drying out as soon as you unseal the container. As someone said earlier, when you seat a bullet, the level of humidity inside the cartridge is essentially locked in. So you open a fresh container and immediately load some test rounds. The test rounds have humidity only a little drier than where the container was sealed, but when you come back days or weeks later, your unsealed Las Vegas jug is a lot drier. Your loads were all 25.5 grains, but the first loads had more water, and the last loads had more powder. You might need to remember to crack open your jugs a few weeks before you start using them.
 
6ShotsOr5? said:
Think about the load as two separate components. There is powder, and some water in the powder. The powder starts drying out as soon as you unseal the container. As someone said earlier, when you seat a bullet, the level of humidity inside the cartridge is essentially locked in. So you open a fresh container and immediately load some test rounds. The test rounds have humidity only a little drier than where the container was sealed, but when you come back days or weeks later, your unsealed Las Vegas jug is a lot drier. Your loads were all 25.5 grains, but the first loads had more water, and the last loads had more powder. You might need to remember to crack open your jugs a few weeks before you start using them.
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I agree with this theory. Not only is it correct, but it is compounded because not only are you loading more of the drier powder by weight, it is, in fact, drier, and will burn faster. More powder, and it burns faster. Yikes!
 
To get a deviation of roughly 60-70 fps from one batch to the next does not indicate that there is any one absolute thing that could have caused it, which would be pure speculation from any of us, I think. I do know that I have loaded a LOT of .223-sized cases and stored for years, sometimes, before getting the big hunt in to expend them all. I live in a "moderately dry" area - but nowhere as dry as where you are. I haven't experienced that kind of velocity change, though it could affect it to a very minor degree. That powder gets sealed up pretty well, and in a few weeks, I'd doubt it possible for that much moisture to escape to affect the velocity that much. I don't know this scientifically - just from my own practical experience. There are tons of variables aside from air temperature, some directly related to minor deviations in the loading process - such as an electronic scale providing different measurements in different temperatures, a change in the lot of primers, change in seating depth, etc., etc. You might be on to something with the case-weld, given it is new brass - as those virgin necks will stick enough to cause additional pressure after a while, though very small in amount for that short time period. In your dry climate and only several weeks, I doubt that was as much of a contributor as other external factors - which could even include a coppered-up barrel, doughnut formation, who knows what all........

In short - if you know your loading process was entirely uniform in how all procedures were completed, same lots of brass, bullets and primers, I'd just back the load off 3/10 grain and see where it shoots next time, as the next question that comes to my mind is if you go shoot that load in the hot weather again, will the velocity ratchet up another 60-70 fps?
 
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