How much powder bar or powder throw adjustment with new powder lots?

[markm87]

I switched lots of CFE Pistol last night that I run through my 550b with the Dillon powder bar system. To my surprise, the weights I was getting were way over my 5.9 gr load on my last lot. It was a beam scale, and I didn't think to get the exact variance, but I'd guess it was .4 gr heavy.

Have you guys noticed that you need to recalibrate for bulk density on new powder lots?

 

[243winxb]

IMR 4198 ( 18.5 gr vs 19.6 gr.) and Alliant 2400 (13.0 vs 13.6) Measure setting at same volume.

There will be a difference in weight, old being lighter. Why? My guess is some of the solvents evaporate in the older powders. Or outgassing??

Dumping 20 drops before measuring, to let powder settle. Using a funnel as a baffle.



Edit/Add I would never mix different lots of the same powder.

 

[markm87]

Crazy. I've been loading for many years, and this never occurred to me. I always re-calibrate on a fresh run of ammo, but a direct lot change was eye openning.