Peter years ago, between wire industry jobs I worked at a place that spun cartridge brass tubes closed. We had two suppiers. Our spec told them what we wanted them to anneal them before shipping to us. one end was made closed and we put a pole piece, a spring, a core and oil and then spun the end shut. We then heated each part to check for leaks.. One batch had near 0 defects per thousands of parts and the other batch had several defects per 100 parts.
I was able to identify that the problem was limited top one of the suppliers. I sent samples to Marshall Yokelson (I used to work for GCC too) he check and said that there was significant differences in the grain size of the unspun tubes. Bottom line was that one had an intermediate anneal and the other didn't. This caused the one with the smaller grain size before spinning to have small cracks, etc. I then spoke to the supplier and learned that while they looked alike they had different mfg. processes that the final anneal did not correct.
Point I trying to make is that the end user should always get with the provider to make certain that the finished products meet the same quality standards in all ways.