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Posted: 1/7/2014 3:33:19 AM EDT
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Well, it is cold as all get out today with sub-20 degree weather here in SC. My reloading setup is in my garage, and it is probably in the upper 30s to 40s in there.
I am reloading 9mm with HP-38. I don't know if it is just me imagining this, but it seems that my powder measure is dropping more/heavier charge. I have the PM set to drop about 4.75 grins of powder and it has pretty consistently dropped this charge +/- .05 grain(4.7-4.8 which is fine for me) through all other weather. But, this morning, I was getting drops in excess of 4.9 grains. Is this(HP-38) or all other powder more dense at low temperature? Is it a metering(PM) problem affected by the temp? Is it all in my head? In any case, the wood knob on the end of the press handle came off in my hand, so I figure it is cold enough to make aluminum contract some(it has never done that in more than 20,000 strokes). I just decided to stop then. |
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If I have to wait for <20 degree weather, it won't get shot because this ole boy ain't goin' shooting in this weather!!!
Best that I can tell is that 5.0+ grains is the max load in several manuals, so I should be fine without worry of over-pressure anyway. Basically, I was wondering if the cold was affecting the powder or the machine. |
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It could be three different things, but one is more likely than the others....
#1 (less likely)... the metal parts in your PM have different co-efficents of thermal expansion, and in the cold the tolerances may change a little causing a slight change in the drop amounts. #2 (more believable).... any lube in your PM has a change in it's tackiness or slickness in relation to the huge temp. drop and changes how much powder sticks or doesn't inside the PM. The low temps may also cause more static electricity and static build-up (dry and cold = lots of static) which would give the same effect. #3 (probable)... you are using a digital scale that is not temp. compensated and it's readings are thrown out of whack. Or you are using one that is temp. compensated and it's not working as well as you would hope. FYI..... I tried using my digital calipers (stored in the garage the other day) when it was really cold and it was acting up to the point I couldn't use it. I took it inside, and 30 min. after it warmed up it worked fine. -ZA |
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Should have noted:
-The PM is the Lee Auto-Disk mounted on a Pro1000 - basically has no metal parts controlling the powder flow with the disks being plastic. -The scale is a RCBS 10-10 that has been calibrated using various weights from 1 grn to 100 grn. So, ZA, of all the "likely" choices there, the only thing could be the plastic disk somehow changing shape due to the cold(which I must agree that is highly unlikely). To add to the temperature extreme, we are have very low humidity levels(30%), so I don't know how that could affect it. I am not sure if barometric pressure would make a difference, but I don't think it is very much different than normal. It must be the powder having a different density with the cold. I know that liquids such as gasoline has a different density according to temperature, but a dry solid!? Did I nod off in science that day?? I have always heard that powder has a different burning rate in temperature extremes(some powders less so than others), but metering different still seems odd to me. |
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Baby steps, my friend.
Before I got married and had kids and built a house, I had a whole bedroom setup for reloading. When the kids came along, it got packed up and moved to the workshop. Then, getting it out of mothballs and setup in the workshop. I made a huge move just getting it back underneath my roof. It wont be making the trip indoors for a few years until the kids graduate to the 2nd floor. One day. |
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