Ruined Brass?

[RetMSgt]

I did some load development for my wife's 9mm yesterday. After getting home, I used a universal decapping die and tossed them into the tumbler with stainless steel media for a quick cleaning. Long story short, I fell asleep.. So they sat in there overnight. I usually only tumble for a few hours at the most.

Ive read a few threads that state ss media will work harden your brass. I don't use it after each firing, every other and I anneal (rifle brass). These were twice shot and roughly around 60 cases. Are these ok to still fire? Or best to toss them out? It's S&B brass. Thanks!

 

[spife7980]

AMP dispelled the myth in their most recent testings, you should be fine to use it. https://www.ampannealing.com/article...he-microscope/

"7. Tumbling cases in stainless steel media does not work harden the entire cross section of the case wall. This contradicts our earlier findings. When hardness testing the neck of an intact case on a mandrel (see photo on left), the diamond indent is made on the outside surface.
Measuring that way shows that 4 hours of SS tumbling hardens the surface of the case wall by 15 – 25 HV. When the same case is sectioned however, the cross section of the case wall can be tested (see photo above right). This showed that no work hardening occurs deeper into the cross section. The tumbling effectively creates a harder "skin” on the surface which is undetectable even under 200X magnification or higher (Appendix 2 - figure 5.1). In all other instances, there has been a very accurate correlation between mandrel and cross section hardness testing."

 

[shoot4fun]

How many pieces are we talking here? If not but a couple hundred or so the just toss them, especially if it makes you feel better.
Otherwise I would not worry about it, assuming you used the standard water, Dawn and a teaspoon of Lemi-Shine.
If it is over work-hardened I would think resizing a couple and checking that it will still hold a bullet should ease your mind too.

 

[918v]

They're fine. I tumble 8-12 hours.

 

[RetMSgt]

Thanks for the answers and help! Excellent info Spife. I used the standard dawn, water and lemishine.

 

[yakstone]

9mm straight wall cases - I would not worry about them at all. Load and shoot.

 

[mdmp5]

First off, tumbling in stainless media will not do anything to brass, other than slightly peen chamfered mouths on rifle cases. Being that this is pistol brass, there won't be any changes to it at all. Pistol brass is quite resilient.