briandg: " When you look at case blowout photos, nothing even remotely looks like mine."
And because of that and your descriptions, a photo of that would be a "one-of" internet classic. Murphy's law tells me that you may not have such a classic photo of it ?
ShootistPRS: "In the last 45 years of reloading I have never had cases shorten regardless of their shape."
I would normally agree with that except for the multiple reload test on 9mm I discussed, where I was specifically looking and measuring everything I could think of. My experience is a few years less than yours, but I have not had a reason to ever trim any pistol case, and I gage check all of them after the resize operation. I will concede that the straight walls like 357 magnum and 44 magnum would benefit from a trim but even if the gage shows a slight overlength there, I simply give those the extra roll crimp they deserve. Which means that I further concede from your entire post that I believe you are a more consistant shooter than I and that you are discussing something which helps your accuracy. For me, the magnums (44 in particular) can use extra crimp since I have never eliminated all the "flinch" when I shoot them. Yeah, Shootist, I am a wimp. I still flinch on the big Mags.
rock185: Entire post is extremely thought provoking. So much that it took me right back to the prior post.
jetinteriorguy: "even at the lowest level of 5gr I had primer flow, tried 5.2 and saw a substantial increase so I shut it down."
This is an excellent example of how any reloader should be conditioned to react FIRST, to anything that concerns you.
Mississippi: "and the federal primers flowed to fill the pocket".
I also agree entirely with rock185. The key for my own understanding is the use of the term "primer flow".
For me, this implies what I would describe as primer flattening, losing its round edge and leveling with the pocket brass edge, or Mississippi's simpler statement above. I have seen this in rifles, but never in a pistol case. What I see in pistols is a flatter than normal primer base which certainly changes the primer look, but not like a truly flattened-across-the-hole primer. With a magnifying glass, I can still see a slight rounding to the primer below the flat area. I see this most with "reduced loads" in revolvers, where the primer pops back, then the case slams back reseating the primer against the revolver receiver. But how do you really know ? Lets talk about "low pressure" signs.
What I usually see with the starting range in pistol load test, (and my argument for clean, not blackened cases), is the slight blow-back marks around the neck of the case. These should gradually disappear as the test load increments. (And usually the flatter than normal primer base will disappear with the blow-back marks.) Now if this does not happen, then I would have to go with rock185 and Mississippi on changing primers. Reading pistol case pressure signs is hard because they are minimal and can be easily argued over. Plus it is usually a sample of ONE. That is why I use multiple guns for load development. One can be a fluke. Three or more is STATISTICS. (BIG GRIN)