I was recently doing rapid firing lube testing in the 38 Special. This involves 100 rounds as fast as they can be fired at multiple targets to see if the lube will hold up. Since maximum accuracy was not required, only relative groups at 25 yards I used mixed cases fired perhaps 15 times with target loads. I got some fliers and each time I looked there a case mouth crack. The cases were inspected after loading and some cracks were found and pulled, the cases were on the way out. The cracks happened on firing, the result was predictable.
Yes the lube worked just fine.
