Same volume of powder, different weight?

[Fitch]

Interesting point fitch, misunderstood it at first aswell. But I reload in my house with aircon so humidy is uniform. The problem I'm having is that when I measure one lee dipper of powder, weight it, then measure another, I get a weight that may be off by a grain or two. I fill the dipper then scrape the excess off with a paper business card. Why are my weights for an equal volume so off? I'm loading for .308win so +/-1grain out of 41.5 is quite a bit.

Oliver

I suspect it has to do with how packed the particular scoop happens to be. Using a volumetric measure, like my Redding BR3, I am very careful to use the same stroke so that the powder loads the same and packs the same in the measuring chamber. I suspect it is hard to be uniform with a scoop.

Note that by pouring powder into a cartridge using a drop tube funnel it is possible to get more in the same volume. this is the same "packing" phenomena I'm talking about.

If you have some ball powder like AA2460, you might do your experiment with that powder scraped level in the scoop. I think it will be more consistant than some of the big stick powders like IMR4350, but still not perfect.

Fitch

 

[MagnumManiac]

Oliveralan,
Have you tried 'tapping' the scoop on the side of a container before you level off the powder?

Many years ago my Grandfather used Lee dippers, he would pour the powder into a glass bowl and dip the scoop in then tap it a few times to settle the powder before levelling it off with a card.

I cannot tell you if this gave a consistent weight to each dip, we had no way of weighing powders back then, but the groups he shot with his 270 were pretty amazing!

Powders don't all weigh the same even when they're the same type.
Specific gravity changes as to how much moisture was present when manufacturing took place, so it's not uncommon to have 2 different lots of the same powder weigh differently.
gun)

 

[Mikecr]

It seems like the question still remains about volume -vs-weight though.
If a different lot produces weight-based loads with different velocity, would this then be corrected by using the same volume-based loads between lots?

A big question for me because to be honest, I can't figure how same volume could be achieved with any precision. Even physically counting out granules per charge might not do it.
Weight seems the only thing consistantly 'measurable' about powder. Especially with extruded powders..

 

[MagnumManiac]

It seems like the question still remains about volume -vs-weight though.
If a different lot produces weight-based loads with different velocity, would this then be corrected by using the same volume-based loads between lots?

A big question for me because to be honest, I can't figure how same volume could be achieved with any precision. Even physically counting out granules per charge might not do it.
Weight seems the only thing consistantly 'measurable' about powder. Especially with extruded powders..

Mike,
You have hit the holy grail!
Measuring your powder by volume is about as consistent as weighing each load due to variances in specific gravity.

As you suggest, if you counted the amount of kernels from a weighed set of powder 5 times, I bet the number would be different each time, just as it would if you did the same with a measured set of powders.

I can tell you this with absolute confidence.
The most important aspect of your powder charging is pouring technique, which is the 'packing scheme' used once the powder is in the case.
If your powder isn't packed the same from shot-shot, it will be more inconsistent than a powder that varies in weight by a few tenths and has a good packing scheme.
I found a long time ago that 'as dumped' charges are more inconsistent in combustion than a charge that has been poured into the case using the 'swirl charge' method.
Even though it's slower than just charging each case with the measure, I dump each charge into the scale pan and pour the powder in with a funnel. I hold it an angle to cause the powder to 'swirl', like a tornado, as it falls into the case.
This allows a much longer time for the kernels to settle and it packs down much tighter in the case without having to resort to vibrating or tapping the case.
I have demonstrated that a charge that is 'as dumped' fills a case well into the neck can be reduced to below the neck/shoulder juncture with ease using this method.
Without any other changes to the load, I have had a reduction in ES's of 75fps and SD's back into single digits after this simple change in packing scheme.
Each charge is still not weighed, but the measure is not altered either, if it happens to be giving me 80.5gr instead of the desired 81gr, I do not alter it to get it!
Whew!
Long winded I know, but hope this clears up a few mythical theories out there about weighing every charge.
gun)

 

[Mikecr]

Sounds like a good method for improved load density.
But wouldn't the packing just swirl to a different case fill with the implied specific gravity variance?
And how could all this be improved on?

I weigh out charges and pour into a funnel with a well hung 12" drop tube(well, thats what she says). But I'm always open to improvement

 

[MagnumManiac]

Sounds like a good method for improved load density.
But wouldn't the packing just swirl to a different case fill with the implied specific gravity variance?
And how could all this be improved on?

I weigh out charges and pour into a funnel with a well hung 12" drop tube(well, thats what she says). But I'm always open to improvement

Mike,
True, but the difference is so minuscule that it wouldn't matter, we're only talking a few tenths here, not the same as a faster or slower lot of powder, which can be as much as 3gr's difference.

I have also found that a powder that behaves erratically can be subdued by a good packing scheme, but it doesn't always work out this way, some powders just don't work no matter what you do.

I don't know how it could be improved upon, but we must be getting close to optimum when we are getting single digit SD's and ES's in the teens, although I have had a few loads that had single SD's and ES's in the past, but they are few and far between!

I too thought that weighing was the optimum method, but soon discovered the above not only improved accuracy, but also stopped a lot of vertical at ranges beyond 600yrds.
I don't do a lot of long range hunting anymore, but still like to ring my gongs at 1000yrds on my own private range.
The last long shot I took at a deer was at a lasered distance of 588mtrs, but I was shooting from my porch, not out in the field.

I haven't discovered it all, yet, but I am forever endeavoring to!
Cheers.