Powder deterioration and impact on loads ?

[284allways]

Gents, I recently contacted the manufacturer of IMR powders over a brown cloud of dust thats been visible each time I pour IMR7828 into my measure. I have been reloading for 40 years and never gave deterioration a thought. All my powder was relatively new, never had ancient powder. Well, so I learned that this brown dust was a sign of deterioration and was dangerous. I dumped the powder immediately.


My question is that when I used this powder in a 300 weatherby, I would routinely get flyers, 1 out of 3 or 1 out of 4 that opened my groups to 1.5" + at 100 yds. The rifle is a very high quality custom rifle and I have Tally mounts, a Leopold that has been checked (sent back to the factory).
Is it possible that powder deterioration could have been causing Velocity E/S and accuracy issues ?
Thoughts and views would be appreciated.

 

[PJGunner]

I think it most likely was the cause due to erratic burning, thus erratic pressure.
Paul B.

 

[ShadeTree]

Short answer is yes. Although to what degree it would cause groups to open up, and how often, is impossible to speculate on. Too many variables.

I ran into the same thing twice, using old metal cans of powder. Powder looked, smelled, and performed just fine. What happened was as I got around halfway through the can, I exposed some light surface rust inside the can at that level. When I would pour powder out of the can, then back in, I was basically sanding that surface rust off which was visible as a brown, dusty, residue left on my powder funnel.

Was getting the same thing as you......inconsistent groups out of a previously good load and rifle using that same can of powder. Bought new powder when I discovered what was happening, problem immediately went away.