Optimum humidity?

[PeteFox]

In an effort to control the humidity in my reloading room I have purchased a room dehumidifier (refrigerated type).
I don't have mushrooms growing out of the walls, it's a dry room, but there is enough humidity about to make a definite change (drop) in velocity as the powder containers empty and moisture is absorbed by the powder.
I don't have primers and projectiles to burn (or the range time) to do continuous testing to adjust to these changes so I'm tying to get a standard set of conditions for reloading.

I've had a Kestrel drop in there for a few months now and relative humidity (R/H) typically varies between 55~65% in a 24 hr period. I put the dehumidifier in there about 12 hrs ago set at 45% and the R/H is now 50% and there is about 1.5 litres water in the catch can. The R/H was 68% at the start.

For those who have done this, what is the optimum R/H for a room that will maintain the as supplied humidity in the ADI powder?
Any idea what ADI say about the effect of humidity?

As a side bonus I think that a drier space will also help look after the electronics. I read an article by AMP that said the biggest enemy of their annealer in longevity terms is humidity and I imagine this also holds true for scales, autotrickler etc.

Pete

[Rich4]

I would suggest with no scientific knowledge that an average between your normal extremes would be the place to start, unless you are travelling to shoot in which case I’d split the average for that location, the suspicion being that consistency is more important than a particular number.

[PeteFox]

Yes Rich,
consistency is important, but I want to be consistent around a particular number. The number being, whatever the powder is packed at, in order to be consistent throughout the 'life' of a jug of powder.
As I understand it, the burn rate of powder (the determinator of all the important things) is altered at manufacture by the addition or removal of water during manufacture. So if a powder is too quick it can be slowed by the addition of water and vice versa
I never leave powder in the hopper, I close the containers straight away. This is leading me to guess? that it doesn't take much absorbed humidity to make a large alteration in burn rate. Large enough to matter anyway.
Over the life of 4kg of 2209 my velocity in a .284 goes from 2820 to 2780 fps. it shoots really tight at 2820 to 2800 and dies at 2780 in my current setup. With the last kilo of powder I'm just wasting components.
I'm going to decant my next jug into 500g containers assoon as opened.
Pete

[Downes Equestrian]

I use Boveda packs to control the humidity when in the jug and hooper. And I check with a kestrel drop. seems to work well for me. as for controlling humidity with a dehumidifier for us out here it is normal for the humidity to be too low. most days in the low 20's so probably would not work.

[Rich4]

That’s exactly how I have always run, however it’s been bugging me for years how to address the problem practically without getting into sealants, as I feel they will have release inconsistencies and sealing between necks does vary

[Weairy]

I'm going to decant my next jug into 500g containers assoon as opened.
Pete

This is definitely a good move. We always decant the 4kg into small containers for this reason.

We run a standard bar type oil heater in the room year-round to keep temps stable and stave off any condensation/moisture (room is a 3x3 ATCO hut outside). Seems to work well.

[Rich4]

I use Boveda packs to control the humidity when in the jug and hooper. And I check with a kestrel drop. seems to work well for me. as for controlling humidity with a dehumidifier for us out here it is normal for the humidity to be too low. most days in the low 20's so probably would not work.

Out of interest which one? I’d never seen such things before, I’ve only used desiccant which is uncontrolled so I have it in a large space.
Vihtvouri recommends 20’C and 55-65% humidity?

[ajvanwyk]

I've done quite a bit of testing on this... Variation in humidity, and therefore charge weight, is a killer to consistent velocity and ES/SD.

I loaded at different humidity (roughly every 10RH%) and found as much as 20-30fps variation. Given that RH could move as much as 30 in a given day, it was clear to me that this was a variable I wanted to control.

I have been fortunate to have a dedicated and substantially sealed reloading room and purchased this unit - https://www.harveynorman.com.au/brevill ... ifier.html You can buy others, but I managed to get this one for a reduced rate and a 5year extended warranty... This meant that it was on permanently, every moment of every day. I keep the temperature to a consitant 21degC

I've set it to a "continuous" setting, which keeps humidity at roughly RH of 45%. Any round I loaded, and every bottle of open powder in that room remained consistent at that rate. Out of interest, in most unopened bottles the RH was 50 when tested.

However, I would not suggest that everyone go down this path... So many other variables need to be addressed first before this "consistent impact" becomes a concern.

Many people (not including the original poster) try to take shortcuts and want the next best thing without ever addressing the most important and critical items first... If there is one thing I have learnt the hard way... that is that there are no free lunches in our sport.

[williada]

Some trivia from an old fart. Circa 2002, I was visiting the Winchester Ammunition factory in Geelong in relation to the testing work for the NRAA I was doing with a view to improve the performance of the ammunition that was to be taken to England by the Australian TR team. Of concern to me was the absorption of water at the high altitude during plane travel. It takes about two weeks for powder to normalize after such flights unless it is shipped at sea level if the ammunition is unsealed.

In the distant past, the issue of fouling also presented a problem with issued ammunition because the sealant had a bitumen base which often required Motty's paste to remove it to maintain consistent velocity which was particularly important at 1000 yards, the championship distance where matches were won and lost. At one time, upon request, Winchester omitted the sealant. However groups in their underground 100 yard test range enlarged beyond their quality assurance standard for dispersion. A burn rate problem? So they decided to go with a non bitumenous sealant. The groups closed up.

So sealant was used with this ammunition along with some suggestions with regard to the manufacturing process e.g. using the same batch of Sierra bullets that came from the same press. At that time Winchester were using Sierra projectiles which were sourced from four different machines producing them. You could imagine the die wear differences on four different presses at Sierra and the effect on dispersion caused by dimensional differences when the bullets were mixed at Winchester. That was sorted.

The ammunition produced was first class because the Poms beat the Aussies with a record score using the Aussie ammo in the Australia match. This ammunition was used by me for the NRAA in testing paired barrels of different twist rates, and bore and groove sizes in order to optimize the relationship between bullet and barrel for the issued ammunition. It was interesting that the issued Bisley ammunition happened to change from the normal Blue or Brown Box Radway Green for which testing was also done. Sourced from elsewhere for the competition? Gamesmanship? It was similar to a story told to me by Percy Pavey when they cut their barrels back in England in the early 1900's to match the ammunition supplied i.e. to make rifles compensate at 1000 yards.

Aside from dealing with the humidity issues, a sealant achieved a complete powder burn. Not that I am advocating the use of sealant today for target shooting, because we can reload the night before a match. But there is a takeaway with regard to powder burn. If you do not jam the projectile, then a maximized powder burn rate can be better achieved with a firmer neck tension rather than a light one. Pressure testing from the machine rest at 1000 yards and 100 yards conducted by me confirmed the matter.

Albert, is certainly on the right track realizing humidity changes during loading have a significant effect on dispersion. While the computer programs indicate that humidity is a small factor in the external performance because velocity changes are less significant, people tend to dismiss its significance. However, humidity does effect the node and tuning point. You may overcome this in the selection of a wide node or utilize an OCW tune or a compensation tune. Note, a tiny powder change or a seating depth change say in the order of .003" can change the tune and yet this is hardly noticed in velocity terms. Its about timing the vibrations at the muzzle and throat which change bore size as well as the barrel lift in relation to bullet exit.

But ask yourself, why under scientific testing, a bullet speeds up a short distance from the muzzle exit? The bullet also has to push the atmosphere from the bore. Velocity will vary on cold barrels. There is a tendency for cold shots to go low unless there is a compensation factor. As the barrel heats friction also becomes less. More importantly, just like Percy Pavey understood positive compensation in relation to bullet exit and muzzle position, the lesson does not end there. The distance from the muzzle to a point where the bullet accelerates varies with barometric pressure, of which humidity is a factor. Believe it or not, the nodal point and reflected vibrations does not end in the steel as commonly thought. Ever wondered why low SD's are not reflected in groups on occasions? Food for thought? Note, that flutes are tuned on the atmospheric node lying in front of the flute. Also note that Obermyer said, his deep hole crown conditioned the atmosphere. A tuner can accommodate the atmospheric changes. It only takes small movements of the variable tuner to accommodate the small changes in humidity in the hands of the experienced. I shall leave you to ponder which effects more significant.

[Peterla]

I don't control the humidity in my loading room and it something I have considered.
As soon as I open a 4kg jug of powder I drop in a Krestral humidity reader and a Guitar storage 50% humidity pack that adds and removes humidity.
I works really well and my 4KGs remains between 49 and 51 % RH
I then only take out what I need to load and I am not sure how quick the power will absorb or give up moisture but I keen the time down to a minimum with the power in my loading setup.
I do not know how well sealed the neck of a case is so if I am traveling I put my rounds in a sealed back with another 50% pack.
Maybe a bit over the top but when I get a flier I know that's not the cause and its probably me.
Its all those little 1% that you can control that sometimes get you over the line.

[Fire Dog]

I do run a de-humidifier set at 55% and have for years to combat the moisture from living near the coast.
No moldy leather goods, drapes don't feel damp and the computer does not need an overhaul every year due to collected dust and damp salt air and loading room is always constant.
I do decant 4Kg powder jugs into 500 gram bottles as I need them, toss in a couple of silica packs to keep moisture down and minimize time powder spent in hopper of powder measure.
Remember, powder also looses solvent if left in the open for any length of time; moisture is not the only concern when loading... Loss of solvent changes burn rates, volume weight too.
Ammo always stored under same conditions as well
On a rainy day I can take as much as five liters of water out of the atmosphere in 24 hours....!! The machine has been worth every ¢ and cost about $1.30 per day to run.

[Fire Dog]

In an effort to control the humidity in my reloading room I have purchased a room dehumidifier (refrigerated type).
I don't have mushrooms growing out of the walls, it's a dry room, but there is enough humidity about to make a definite change (drop) in velocity as the powder containers empty and moisture is absorbed by the powder.
I don't have primers and projectiles to burn (or the range time) to do continuous testing to adjust to these changes so I'm tying to get a standard set of conditions for reloading.

I've had a Kestrel drop in there for a few months now and relative humidity (R/H) typically varies between 55~65% in a 24 hr period. I put the dehumidifier in there about 12 hrs ago set at 45% and the R/H is now 50% and there is about 1.5 litres water in the catch can. The R/H was 68% at the start.

For those who have done this, what is the optimum R/H for a room that will maintain the as supplied humidity in the ADI powder?
Any idea what ADI say about the effect of humidity?

As a side bonus I think that a drier space will also help look after the electronics. I read an article by AMP that said the biggest enemy of their annealer in longevity terms is humidity and I imagine this also holds true for scales, autotrickler etc.

Pete

YEP! See my comments at the bottom... Exactly right about the humidity.
Have both Auto Trickler and an AMP annealer as well as computer electronics... ALL have benefited from lower {I live near the coast} and controlled humidity....