When steel pin media is new it has sharp corners and these peen the case mouth
Yup. Camera work today comparing a sample pre-vs-post
rotary case cleaning clearly shows peening of the case mouth after the rotary action
. That fully explains the 3 thou change in neck internal diameter only.Ordinarily my case prep sequence is de-prime, ultrasound bath, hot fan dry, anneal, resize, trim, chamfer.
These rotary tumbler test cases were unique: they had already undergone the process in the previous sentence when I dropped them into the rotary tumbler. So not in a typical state prior to cleaning.
Now that I know that the rotary drum wet cleaning with steel pin media does cause neck peening, I realise that it has to be followed by chamfer.
But...what rotary drum wet cleaning with steel pin media also does is remove the annealing high-tide mark. Which makes for a prettier case
. So the sequence I will probably use [compared to my old method] is as follows:Method #1 -------------------- de-prime, ultrasound bath, hot fan dry, anneal, resize, trim, chamfer
method #2 -------------------- de-prime, anneal, rotary tumble, hot fan dry, resize, trim, chamfer

