It all depends on what the atmosphere was like where those case sat for 5 days. Typically, moisture content for powder coming from the factory is around 40-50%, depending on the particular powder. If the humidity in the environment was substantially higher, or lower, that moisture content will likely have changed accordingly. Lower moisture content produces faster burn rate which can equal faster velocity and higher moisture content will be the opposite. If you're loading those cases where they're HOT loads, and the moisture content had dropped significantly, there could be an over pressure issue. Otherwise, there should be no other issue as additional moisture content from what you had would simply produce slower velocity and likely change POI from what you'd expect. . . particularly at distance.
Yes.
How far we take "airtight" depends on the specification.
Right. So, if it's not air tight, how much does it matter what the % humidity is at the loading bench?
It's not air tight in this case because the OP said he charged the cases but did not seat the bullets. So the powder was exposed.
Imagine the time constant. There is a rate at which the internal volume will change, and it is far from instant.
LOL, no. Far from air tight unless we use sealant, and your friend just got lucky.
You may be right, just going by that one experience. This ammo was in the rain most of the day before he realized it was out there.
I think a lot depends on the difference in atmospherics from where you load to where you take the cartridges (and how the transport container is sealed or not). The difference in atmospheric air pressure and the pressure within the cartridge will induce movement from the higher pressure to the lower pressure. If the outside atmospheric pressure is less, the movement of the cartridge interior air will move to the outside until it stabilizes. When bullets are seated, there's some pressurization of the air inside and movement will occur immediately, but to no effect. At low difference between the inside and outside pressures, the movement will be rather slow.
We test ammo and ordinance at specified pressures. We submerge the ammo and pump down the pressure to observe bubbles.
The Armory was dry, just not climate controlled, and with it being in Georgia, there were large humidity swings. Most of the ammo was stored in ammo cans, but lots were simply kept in magazines on racks and were handed out and turned in every shift.
