Most bench shooters will tell you that volume is the more accurate means for measuring charges than weight, well today I made an observation that vindicates this for me.

Last night at 3am I loaded 50 .32acp using 2.2grains of WW231 using my uniflow powder measure with a micrometer metering tube. When I set up for this load I looked at my log book and set the measure to 003.5 that I had been using all along for this load. Upon double checking with my Ohaus balance and a cheap digital both scales concluded that I was about 0.2 of a grain light at 2.0g by weight, after some deliberation I decided to believe my notes and uniflow and loaded up 50 rds on the 003.5 setting I had always used. When finished knowing I would load more when I woke up I left everything as it was capped off the lid on the powder measure closed the door and slept til noon.

fast forward to 2:00 PM today loading up another 50 rds with the uniflow still set at 003.5 untouched from earlier both of my scales now say that the charges thrown weigh the desired 2.2grs

SO what happened in that time period when away from my loading gear, either.


A changes in humidity effected both scales <doubtful>

or
.
B the weight for a given volume of ww231 changed for some reason or another

Also be mindful that my reloading operation is inside a climate controlled room

scientific: not hardly but interesting none the less. Anyone else made similar observations or just care to speculate

Powder settled a bit after sitting in the measure overnight????

Climate controlled or not, could be some more humidity absorbed into the powder perhaps.....

I seriously doubt the powder absorbed enough water to change its weight by 10%. If it did, your powder is wet...

2.2 grains is a very small charge. The 0.2-grain variation in so small a charge is a large percentage of the charge. To check your scales, throw a large charge and weigh it (the same charge) ten times. Find a descriptive statistics program on the web (I found one quite easily for this very same purpose) and run the stats for the charge. If you get an SD of very little, you know your meter is throwing well. When I throw a charge I tap the powder measure before the throw to pack the powder, swing the lever down and tap again after to empty the cylinder. I get very consistent results. When I do not, I am all over the highway.

http://www.physics.csbsju.edu/stats/cstats_NROW_form.html

Sleep loading...

Two different things going on here. One is the powder measure itself and the other is the consistency of the technique used. The concensus is that the best one can expect is 1/10 of a grain accuracy from a good powder measure. For a 2 grain charge, that is a lot! For a 32 grain charge that benchrest shooters use, it is acceptable bearing in mind that shooting technique, wind reading etc. are much greater sources of error. I do not throw charges that small. However I do throw charges of 2.8 grains of Bullseye for my 38 Spl. target loads and have not noticed any accuracy variations that I could attribute to the powder charge. Much more likely to be my aim, trigger pull etc.
Peter.

I have found after years of loading that once a load is worked up, the velocities are more consistent when I set the measure by volume than by weight. This is especially true when changing powder lots, etc. The difference in lots will vary more by weight than by volume, for whatever reason and I suspect this is why the benchrest shooters do it that way. They don't want to rework their killer load every time they are forced to change lots. Homebrewer is giving you some good info also, by using a tap to settle it I can throw +- 1/10 grain, otherwise it is about three times that amount on a 70 grain charge.

many moons ago our rifle club bought a crono for members use. we proceeded to load about 16or 18 different calibers with measured and weighed powders, both ball and stick. using velocity as the measurement and using 5 round tests, we found that the closest velocities came from measured ball, then measured stick, then weighed ball and last weighed stick.. if i remember right the measured ball got 5 rounds 5 fps apart at best, and at worst was weighed stick which hit about 300 fps apart

Peter is right. Volumn charges are only as accurate as your technique. A weighed charge is a weighed charge, as long as the scale is accurate, then so is the charge wt. I use both methods & have success to 1/10gr which is about all you can expect.

quote:

Originally posted by butchloc:
many moons ago our rifle club bought a crono for members use. we proceeded to load about 16or 18 different calibers with measured and weighed powders, both ball and stick. using velocity as the measurement and using 5 round tests, we found that the closest velocities came from measured ball, then measured stick, then weighed ball and last weighed stick.. if i remember right the measured ball got 5 rounds 5 fps apart at best, and at worst was weighed stick which hit about 300 fps apart

I've met this guy and truly believe he'd not pull our leg.....seems like a fine fellah

I also believe he's telling the absolute truth here....I believe this is exactly the result of the test.

That said.....I'd dearly love to know how this can be......assuming all powder tested is of the same lot/batch/canister. It's totally illogical!

If you hop over to http://benchrest.com/forums you'll see more and more people gravitating towards pre-WEIGHED charges. This as opposed to charges measured volumetrically - mostly through Harrel's measures, the traditional tool for bench resters.

Traditionally, bench resters have expected to "tune" a load to the conditions on a given day. On the benchrest.com forum, this is now (or sometimes?) interpreted to result from changes in the results of volumetric measuring under different atmospheric conditions. Some believe pre-weighing charges gets rid of the need to tune the load on a given day.

I don't want to give the impression I know which method is best, but it seems there are people in the know who use either method.

- mike

The missing factor might be % of case volume.
I have often wondered if angle of repose at ignition would affect the pressure curve. I would expect it to but don't have data.
I try to use powders that give 95% to compressed loads as it related to volume. This should give the advantages, if they exist, of both worlds.

All may be fine for benchresters to use thrown charges but for cartridges used for long range shooting with stick powders the best and most uniform (ES and SD) loads (that reads "the most accurate loads") come with weighed cahrges.

Larry Gibson

The velocity produced comes from the energy produced.
The energy produce comes from the mass of the powder burned.
The only way to get the same mass is to weigh it.

The only improvement I can think of would be to weigh volume thrown charges and use only the volume thrown charges that weigh the same.
The assumes you get exactly the same kernel count per unit mass. Too much trouble for me.
Eventually I have to get to the range.

quote:

Originally posted by butchloc:
many moons ago our rifle club bought a crono for members use. we proceeded to load about 16or 18 different calibers with measured and weighed powders, both ball and stick. using velocity as the measurement and using 5 round tests, we found that the closest velocities came from measured ball, then measured stick, then weighed ball and last weighed stick.. if i remember right the measured ball got 5 rounds 5 fps apart at best, and at worst was weighed stick which hit about 300 fps apart

Hey Butch, Excellent "First-Hand Test" input.

The thing that ALWAYS interests me in this kind of discussion is that everyone has the ability to try it both ways(Volume vs. Weight) and see what works the best for them. And yet, when someone speaks up who has done an actual Test, with 16-18 cartridges, there are people who have never done the Test, that will argue about the Test results. Not trying to understand what the people doing the Test did, not asking how they went about it, just stating words to the effect that they can't possibly be right.

Amazing!

Now I really doubt I could defend myself against enemies who looked this good!!

Marion
Did you take that picture of BHO yourself?