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Hornady LNL AP Press Power Measure Temperature Sensitivity?

1K views 4 replies 4 participants last post by  Rick.T 
#1 ·
I've run through 45K rounds of 9mm on my press with the micrometer-adjustable powder measure. I've found the powder measure to be very, very consistent and using the micrometer to be reliable although I certainly check when re-adjusting. I'm loading currently with VV N320 and set up this am in an unheated out-building, approximately 35 degrees, and the drop has shifted by perhaps +.15gr from my last session a few days ago under considerably warmer conditions. Has anyone else experienced this? It's not a big deal using the measure twice/cut once philosophy, but it's not something I would expect.
 
#2 ·
probably has more to due to changes in humidity than with temp. Also, if you are using an electronic scale (which I do) they will fluctuate until warmed up.

I, too, reload with an LNL in an unheated detached garage - have to run a space heater when it gets down to the 20's.

Anyway, when the weather is going to vary considerably I usually put the powder back in the original container rather than leaving it in the powder measure.
 
#3 · (Edited)
Smokeless powder is hydroscopic and that does cause weight variations. I live very close to the Gulf of Mexico so the humidity is always high and I reload in an unheated or cooled garage. I weighed 50 grains of powder and let it set in an open container for three hours. It gained 3 gains in the first hour and a total of 5 grains over the three hour period. I've tried that with CFE223 and bullseye. Bullseye didn't gain as much as the CFE223, but It still gained about 3 grains over a three hour period.

Edit - I just weighted out 67.22 grains and will let it set in the open for 3 or 4 hours to see how much it gains. The last time was in the middle of the hot summer when the moisture content in the air was higher than it is now.
 
#4 ·
0.15 grains???

How do you know you scale is not drifting over temperature. Get yourself a Lyman weight set and compare the reading you get between temperature variations. Most of the electronic scales on the market place are no better than + or - one tenth of a grain. It takes variations of several tenths in the powder load to even see a difference on the target. When searching out for the best load for a particular cartridge I don't even try changes less than a half a grain for rifles.

Read the specs for your scale. Regardless of the number of decimal places you can read, that is not the accuracy of the scale. Add to that if commercial electronic parts are used (as compared to military parts) their spec's are only guaranteed down to 32 degrees F. 35 degrees F is mighty close to that.

http://www.midwayusa.com/s?userSearchQuery=lyman+weight+set

LDBennett
 
#5 ·
I got the same measurement on both my inexpensive digital scale and a 5-0-5. I didn't measure down to .05. The prior charge was 3.7 plus about a index width on the 5-0-5. The second measurement, one day later, was 3.9 "exactly". I did check the 5-0-5 just the other day with my Lyman weight set:). Probably not worth starting a thread on this, but I was curious as to what might cause a small shift in measured charge weight. We do run pretty close to the minimum powder load that will cycle our 9mm 1911s so there is a bit of concern associated with a 0.1gr shift.
 
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