[Unclenick]

Whistlebritches,

A lot of old data was developed in production firearms by watching for brass pressure signs. Before liability lawsuits became an everyday thing, a lot of that data was never pressure tested and that which was tested was done by copper crusher. In the modern equipment age, the graphical piezoelectric transducers have revealed pressure spikes and other anomalies with some of the old data that a crusher cannot reveal. There can also be absolute pressure differences due to burn rate being less well controlled back then, so a bullet company might buy an extra slow lot of something for its manual load development and not realize they were recommending loads that were warm for a more average lot. So unless you have the same gun and components the original data was developed with, you can't be sure it is good and modern data is typically safer.

The way to handle that is to look at the old and the new data and use whichever one is smaller, at least at first.

Powder has a number of failure modes as it ages. Board member Slamfire has posted photos of a number of guns blown up by old powder as well as Navy testing which showed pressure going past proof load levels with aged powder. What has happened in those instances is the stabilizer, which scavenges acidic nitrocellulose breakdown products before they can go on to damage still more nitrocellulose, and the acid products, before weakening the powder appreciably, has first attacked the deterrents in the powder, causing the powder burn rate to increase a lot. Later on, it will weaken so the faster burn rate is no longer able to make excessive pressure, but there is a period of time in which it turns into a bomb.

That effect is caused entirely by heat, not moisture. So if the powder was allowed to get warm, beware.