Dumb question: I have only been reloading for six months. I have gone through about 12 pounds of powder, mostly IMR 4350 and IMR 4064. I have a RCBS uniflow that I added the micrometer adjust to repeat settings. I have noticed that the settings are pretty repeatable as long as I remove the "backlash". One thing that I have noticed is that when I first open one of the cans of IMR powder it has a pretty strong smell. Over a few weeks the smell gets considerably weaker. I am closing the bottles tight. When I first open a can of IMR it seems that the powder is denser in that I have to reduce my micrometer reading slightly to get correct powder charges. Is this really happening or is this just my imagination?

And your thinking is that it is getting weaker because whatever is causing the oder is vacating taking its mass with it and changing the dencity. Well you are right but I doubt if the weight (mass) of the gas is measurable with the equipment we reloaders normally use. Than again your can may have the either just slushing around in
it. You could put a fair amount on your scale and record its weight every day. roger

Does you Uniflow powder measure have a baffle?

The Redding BR3 & Dillon precision powder measure have one it helps keep the powder from compacting in the bottom and helps it give more consistent throws.

My old Redding and Uniflow don’t have a baffle but I measure every charge for rifles any way.