Leaving Powder in the Powder Thrower

[Gregory Gauvin]

I know none of us reloaders ever leave powder in our throwers with a label on it, perhaps with a bag over it, to come back later - the next day, or whatever and finish up a batch. Leaving power in an unapproved container in a no no and powder is hydroscopic.

So we have all done it. However, I was working up loads and carefully measuring all my charges and also taking note on where my micrometer of my thrower was compared to the charge weight. When I came back 2 days later to continue, I didn't just start throwing powder. I through some charges and measured the weight.

To my surprise, none of the micrometer markings I had made the previous day resembled the charge weights I had previous thrown. Example - lets says "NOTCH 4" threw 4 grains, and "NOTCH 6" threw 4.2 grains.

I checked my scale, zeroed it, and to throw a 4.2 charge 2 days later, I though my micrometer would be in the vicinity of where it had been earlier, but I found to throw 4.2 grains, I now had to move it to "NOTCH 8".

Is there an explanation to this? The powder in the thrower was covered, I placed a bag over the thrower...my scale was put away...no dust accumulated on it. I can't fathom as to why such a change was needed to throw the same weight charge.

If powder absorbs moisture, shouldn't it weight more? Instead of increasing my dial to through the same weight, shouldn't I have had to reduce it?

[44 AMP]

The "head pressure" changed.

The same effect, for a more visible reason happens when the hopper gets low, and when you refill it. Some measures have baffles in them, to minimize this effect.

When powder sits for a time, like a couple days, it settles, and becomes more compact. So the effective weight of the powder changes slightly.

It does this in the can, too. We never notice it because pouring it from the can to the measure "fluffs" it up.

Most granular solids behave this way.

Look at a box of cereal. The really do fill them to the top in the factory. But by the time we get it, "contents may have settled".

Unless you are in a high humidity environment, I seriously doubt it has anything to do with moisture.

[skizzums]

Yup. In humid weather I will notice a change just overnight. I have found myself making slight adjustments even with 4 hours or so at the bench. The worse being fluffy flattenedflake powder. I still leave powder in the hopper if just for the evening though. My thought being, I am only going to get LESS of a charge, nothing dangerous.

[Snyper]

So we have all done it

I've never left powder in the measure for more than an hour if I wasn't loading.
It's too easy for things to happen that won't let you get back as planned

[higgite]

You guys are explaining why powder gets more dense if left in the hopper for a night or two, but Gregory's experience is the powder got less dense. I don't have an explanation for it.

Gregory, what did you use to weigh the charges? Did you check it with check weights at the beginning of both sessions?

[9mmSkeeter]

Um, I always do. Never saw a problem. When I began buying more types of powder I labeled the hopper. I pour about 1/4 full and do about 100 rounds a crack.

Edit : I guess that only leaves a small amount in the hopper, lol. But still.

[madmo44mag]

Large shifts in atmospheric pressure could cause a slight change is weight.
It would need to be a pretty wide swing but that happens when weather fronts roll in.

[mikld]

Quote:
So we have all done it

I've never left powder in the measure for more than an hour if I wasn't loading.
It's too easy for things to happen that won't let you get back as planned
__________________

+1,111! I was taught very early (like 7 or 8 yrs. old) to always clean and replace a tool when I'm done using it, by my father who was a mechanic during the depression when tools were very difficult to come by. Sixty years later I still abide by that "law". And 98% of the time I know where to find a specific tool (the other 2 percent is due to fading memory, but I know where it's supposed to be!). Put last reload in a box, put label on the box, empty the powder measure into the lone powder container on the bench, and replace powder container in the cabinet...

[kostner]

Have two SDB's that have had powder in the hoppers for over ten years without any noticeable changes. The powders are W231 & Unique and I live on the southern coast of California. Almost for forgot the Hornady powder measure that also remains full with IMR3031 and drops a steady 22.5 grains. Just don't see the problem with leaving powder in them.

[Clark]

You guys are making me feel guilty.... ok, I am loading already.

[Gregory Gauvin]

I used a calibrated balance beam type scale. I double checked this with a digital scale as well. I fully understand powder becoming more dense. But like one poster stated, the powder in the hopper became less dense. I had to increase the throw to attain the same charge weight. I could understand small fluctuations of .1 or .2 grains letting the powder sit - but, I checked, and triple checked when I first started loading that a NOTCH 4 I was throwing 4.0 grains of RED DOT. I worked up loads to 4.5 grains. I found that each half click adjustment (4, 4.5, 6, 6.5, 8, 8.5 - the numbers go up like that, 0, 2, 4, 6, 8) I would gain .1 grain. For at NOTCH 4 I was throwing 4 grains. NOTCH 4.5 4.1 grains, NOTCH 6 4.2 grains, NOTCH 6.5 4.3 grains, NOTCH 8 4.4 grains.

I found my best loads were 4.0 grains, and 4.4 grains.

I decreased my OAL from 1.245" (shooting 230 grain LRN hard cast Berrys) to 1.243" - only 2 thousands, not significant, but my chamber is tight and I'm seating the rounds just kissing the rifling. A few 1.245" rounds didn't go to full battery, I found all I needed was to decrease it to 1.243".

So, I go back to loading 2 or 3 days later. I figure, I had left the thrower set at NOTCH 8.5 (4.5 grains). I wanted to make a batch with 4.3 grains. So I figured, I have to set my dial at NOTCH 6.5.

I double checked my scale was zeroed, triple checked, checked on my digi...and lone and behold, at NOTCH 6.5 I was throwing charges less than 4.0 grains. I finally set it to NOTCH 8 and measured and measured again and was throwing 4.2 grain charges. I though this to be "odd". I figured, if anything, the powder would absorb moisture or settle and I would have to reduce on the dial.

Any input here or is this an unsolved mystery?

Furthermore, setting your powder thrower to your charge of like, loading 200 or 300 rounds, and coming back the following night to finish off a batch of 500 without checking the throw weight - even though nothing was touched - could potentially....blow your gun apart if you're around max loads. WHAT A LESSON!!!

[44 AMP]

Any input here or is this an unsolved mystery?

I don't know if it will solve your mystery, but here's some input...

measures throw charges by volume. Not by weight.

And, remember we are talking about very, very small amounts of things here..
We adjust the volume of the metering chamber for the weight we want. Changes in the powder in the hopper affect how "readily" it drops into the metering chamber.

Stick powders are notorious for misbehaving in powder measures. Flake types are a bit better behaved, and ball powders measure like water. Nature of the beast.

The old Ideal (Lyman) powder measure had a knocker on it. Some people rap the handle twice on the down (or upstroke), to give the powder a slight jar each time. Helps to prevent "bridging".

Same idea with throwing a few "settling" charges when you refill the hopper. It can take a few dumps before things settle out to minimum variance.

and its ALWAYS a good idea to check what your system is actually giving you, before you start charging cases.

[Clark]

This thread made me feel guilty about my RCBS uniflow filled with H110 for a week next to my desk. So I loaded 180 rounds, and the hopper is now empty. It was painful at 2 rounds per minute. I watched TV on my computer: Forensic Files and RedEye.

It was belling the case mouth that my fingers were procrastinating.

[Gregory Gauvin]

I always throw 3-4 before weighing the charge. I know it takes a few throws before the powder thrower "settles" in. After making an adjustment on the dial, I always throw 3-4, dump it back in the hopper, then weigh it out.

Granted, we are talking about minute differences here. But with RED DOT, a fast powder, (I believe it's a flake powder), a difference of .2 grains makes a substantial difference. My book gives a max load of 4.0 grains at 1.190" for a lead 230 grn bullet. I'm seating longer, at 1.243", so that in itself reduces pressure and could bump the max charge up ever so slightly. I found 4.4 grains to be my max. But .2 grains more, at 4.6grns, I begin to see primer cratering. Seems like to keep my charge exactly at 4.4 grains and load consistent accurate ammunition, not only would I have to clear out the hopper and weight my throw every time I come back to finish a batch, I would have to keep the hopper filled exactly to the same level throughout my loading process. Watch for barometric pressure changes and humidity fluctuations.

Granted, if I had access to my usual powder (HS-6) a .1 or .2 grain difference is negligible in .45 ACP, but, fast powders like RED DOT develop pressure signs rather quickly with a mere .2grn charge difference. HS-6, a slow powder, seems to be very forgiving - as a matter of fact, I have never observed the start of telltale signs of pressure with that powder even past published max loads.

[Sport45]

If powder absorbs moisture, shouldn't it weight more? Instead of increasing my dial to through the same weight, shouldn't I have had to reduce it?

Maybe the relative humidity was less than the last time you had the powder out so it dried out a bit?

I don't buy the hydroscopic business. Powder is more like a plastic than a desiccant. In your case I wouldn't have felt compelled to change the measure unless you though someone had fiddled with it. If you were dumping XX granules of powder today and it weighed 4.1 grains, and it takes YY granules (a different volume) to make the same 4.1 grains tomorrow are the charges really the same? I mean really, if all you've added (or taken away) is water?

[jdscholer]

I one time left my Uniflow sitting with the hopper about half full of (I think) Bullseye. Life took over, and I didn't get back to do any loading for a couple of weeks. When I did, I found that the powder had tried to dissolve the surface of the plastic in the hopper. Granules were stuck on the surface, and had caused actual damage to the plastic. I cleaned it up as best I could, discarded the powder, and quit being lazy. jd

[Taroman]

We all don't do it.
I did that once, many years ago.
Ruined the hopper.
Learned my lesson.
Didn't do it again.

[snuffy]

The term for a substance that draws moisture from the air is hyGroscopic. There's no such word hyDroscopic.

Hygroscopic means powder would draw water in a vapor form from a humid environment. IT DOES NOT! We get caught up by the lingering facts/myths from the black powder days.

Some that buy into the water adsorption have conducted tests where powder was left in a very humid environment, measured, then loaded in a very accurate rifle with a proven load. The same powder was exposed to very dry atmosphere, weighed, then loaded with the same specs except the amount of humidity present when being loaded. Results were the SAME! Velocity, group size, all the same. In that specific case, it made no difference.

When I did, I found that the powder had tried to dissolve the surface of the plastic in the hopper. Granules were stuck on the surface, and had caused actual damage to the plastic. I cleaned it up as best I could, discarded the powder, and quit being lazy. jd

That's because bullseye is a double based powder, the nitroglycerin content is pretty high. The nitro is a good solvent. The plastic hoppers can take some contact with it, but leaving it in there will cloud the plastic and some powder will remain stuck to it.

[Clark]

I have become more tolerant of my RCBS uniflow green plastic hopper being etched by powder left in there, than I am by sawdust left on the table saw and picking up moisture in the air and causing rust. The etched hopper cannot hurt me, the rusty table saw is a drag.

The only reason I feel guilt over powder left in the hopper is that the low vapor pressure solvents may leave the powder when not in a sealed container. That degrades the powder.

[polyphemus]

OP wants to know why leaving gunpowder in the hopper for a couple days results in inconsistent throws.A fellow poster adds that he watches TV shows
while reloading.Both practices are specifically advised against in every reloading guide I've read,the real mystery is: what's the point in doing it?

[JeepHammer]

Respect for all here,
Since this has turned into a 'Technical' thread,

The spelling is wrong, the word is spelled 'Hygroscopic',
The ability to absorb and hold water out of the atmosphere.

I've found several reasons I *Think* might be acting on my powder in the same way, both lightening the charges and making them heavier.

Powder will settle, become more dense when left sitting,
The natural vibration of the earth/house will shake the more dense powder to the bottom, Packing the charge.
The 'Dust' is usually heavier than the actual 'Powder', and when you get to the bottom of the can, it gets heavier QUICKLY...

Rolling the powder can around a little bit before you start will give you more consistent charge throws,
That's pretty well documented...

The baffle in the powder bin will keep excessive weight from packing charges, as mentioned before.

I found out bench loading that a thrower will NOT maintain consistent charges,
And any bench loader that measures each and every charge will know this.
If they did, we wouldn't need powder trickle devices...

I check about every 20 to 50 rounds when loading common ammunition,
And learned to keep a baffle in the powder bin when throwing charges.
I also don't dump the bin full all at once, I add as needed, keeping the weight on the column reasonable,
And that seems to make the throws much closer.

I find a HUGE difference in stick powder and ball or flake powders.
The stick powders will throw with a MUCH wider range.

I chalk that up to the way the sticks fall into the charger,
If they pack well, you get a heavier charge.
If they don't fall well, you get a light charge.

It's just one of those things...

And just for the record, the factory loaded ammo is WAY DIFFERENT in charge weight,
I bought some loaded, then changed my mind about the bullets,
Pulled the bullets, and just out of curiosity, I weighed the powder charges...
As much as 4.5 grains off between light and heavy!

[billcarey]

Wow, been reloading about 30 yrs and leave the powder in for months at a time...probably done years at a time when I was shooting weekly and just refillling the powder. I only take it out when I need to clear the bench for a project. Regardless, I calibrate my scales and check weight everytime I start a reloading session. Can't remember the charges changing either. The only downside I've seen is the powder darkened the RCBS clear hopper so much on one (not both) its difficult to see the powder. This is in Florida and my reloading bench is in my unairconditioned garage.

[Crankgrinder]

I dont do it it's just not a good practice. Original containers only and ONE can of powder in the room at a time.

[44 AMP]

And just for the record, the factory loaded ammo is WAY DIFFERENT in charge weight,
I bought some loaded, then changed my mind about the bullets,
Pulled the bullets, and just out of curiosity, I weighed the powder charges...
As much as 4.5 grains off between light and heavy!

The powder used in factory ammo is what is called "non canister grade". This means that the particular powder does not have the correct specs to be canister grade powder.

It may look smell and taste just like Bullseye (or any other powder) but something about it is too different from Bullseye for it to be sold as Bullseye.
Usually tis the burn rate.

What factories do, is buy this powder by the ton (literally) and develop loads to meet specified pressure and velocity standard with it, using that load (charge wt.) until that batch of powder is all used up. And the process is repeated with each batch of powder.

So, lot#12345 ammo might have 4.0gr, lot#12346 might have 4.4gr, and lot#12366 might have 7gr of powder that all LOOKS identical. And each round will have the same pressure and velocity (within production tolerances) despite the fact that they have different powder charge weights. Because each "batch" of powder is at least slightly different, and can be quite a bit different and still used by the ammo factory after they have developed a load for it, batch by batch.

[Panfisher]

Heck a couple times for very short periods I have left two different kinds of powder in the thrower at the same time. Usually accompanied by cursing loudly.