Inconsistent 38-55 cases from W-W?

[Kraschenbirn]

Was loading small batches of .38-55s to chronograph...same powder charge/boolit but different primers, with and w/o paper wad over flash hole...and noticed that some cases seem to have slightly less capacity.

Cases were freshly trimmed and charges of (sifted) Goex FFg very carefully measured before loading using 24" drop tube but, now and then, powder level in a case (before seating overpowder wad) would appear approx. .060"-.075" higher than the norm. Dumped the first two that I noticed and checked charges for weight but found them within +/- .1 gr. By the time I finished, I'd found a half-dozen more for a total of eight out of the hundred cases I'd prepped for testing.

Went ahead and loaded the "small" cases but marked them with a Sharpie and will chrono them separately and compare readings against those for "standard" cases.

Curious if anyone else has encountered this?

Bill

[August]

I have always been amazed at the different column heights of hand weighed, 30" drop-tubed charges of black powder. The difference in height has always been substantial enough to see with the naked eye -- certainly a lot more difference than you report.

After seating an over-powder wad and compressing with a compression die, they're all the same height. They result in single digit standard deviations. And, they shoot better than I'll ever be able to benefit from as long as I'm the one pulling the trigger.

Hope this helps.

I guess you'd have to fill the cases with water and measure the weight to convince me its the volume of the cases that is the issue rather than natural variation in the volume of black powder when measured by weight.

Herein lies the reason for the "big boys" charging precision loads by weight rather than volume.

[John Boy]

...and noticed that some cases seem to have slightly less capacity.
Krasch, take 2 cases, a 'less' capacity and one of the other 92 cases. Fill each case up so the meniscus of the water is exactly at the mouth of the case. Pour out the water from each and weigh it. You will find out the capacity differences

One gram of water is equal to 1 cubic cm, so you can determine the volume of each case

[montana_charlie]

...and noticed that some cases seem to have slightly less capacity.
Did you weigh your cases after trimming?
If what you think turns out to be true, the small capacity cases will have more brass in their construction. A scale should show that.

If you were chronograping simply to learn 'average velocity', you wouldn't have to be very careful in loading. But, your goal is to see variations caused by primers and primer wads.

For checking something that 'small', I would weigh everything that goes into a loaded cartridge...certainly the case...and maybe even the steenking primer.

CM