Old primers and tarnished Brass

[DLS]

The major "reasons" given to not tumble loaded rounds are that it will unseat the primer pellet and it will cause the retardant coatings on the powder kernels to degrade causing the powder to burn more quickly.

Both are false. The retardants are applied to the powder kernels by tumbling. Factory ammo is tumbled as a final cleaning and polishing step prior to packaging. And ...

Think of the amount of vibration imparted to ammo sitting in the feed boxes of armored vehicles or even more so, the piston driven fighter aircraft of WWII. This amounts to magnitudes more vibration compared to the amount one would impart in a case tumbler. This ammo functioned just fine after suffering much more "abuse" than we are talking imparting here.

 

[DLS]

I once found a stash of primed .44 Mag brass that had somehow found it way into the back of a shed, for like 25 years. It was totally tarnished and had suffered through the humidity and temperature swings common to an uninsulated outbuilding.

All fired just fine. Primers are well sealed at the factory and have good longevity, even when poorly stored.

 

[Mikej]

Think of the amount of vibration imparted to ammo sitting in the feed boxes of armored vehicles or even more so, the piston driven fighter aircraft of WWII. This amounts to magnitudes more vibration compared to the amount one would impart in a case tumbler. This ammo functioned just fine after suffering much more "abuse" than we are talking imparting here.

I'd never though of that. Good point.