Originally posted by cw2go
By full lockup, I mean locking surfaces fully and completely engaged as required to take the full design pressure of normal firing, plus the design safety margin (which should handle significant overpressure for proof firing). At 1/16" back, it is close to lockup, but has just started disengaging (which I suspect is significant), and you can still pull the trigger, so you could conceivably get a kB! in that condition.
The most common kB! is not a failure of the barrel, slide, or frame, but a case failure in the unsupported area at the feed ramp, which is obvious if you examine a failed case or check out the pictures. (This differs from the original post here, which defines kB! in a manner contrary to that of the person who defined the term, who'se site URL I posted above.)
You can test your own pistol (AFTER confirming it is unloaded) by gently pressing back the slide and verifying where it reaches the point where you can no longer get the trigger to release. Once I get the upgrade kit installed (which includes 6 parts: a new Extractor, Spring-loaded bearing, Firing pin safety and spring, Firing pin / striker, Trigger bar) I will run the test again to see if reductes the distance above.
I think that you pinpointed the key issue - though with Walter gone, I am only interpreting his post.
I am sure that as you state he intended KBs to mean only the barrel/slide failures - case failures are (under this definition not KBs, but rather ammo failures)...
Regarding the "out of battery" experiences, the high speed photos that I've seen show the bullets leaving the barrel (and I assume pressure falling to near zero) before there is any movement of the slide relative to the frame and barrel.
This is why I feel that if the breech is tight against the barrel then the slight backward downward movement that is possible is not significant.
From my reading of your URL reference, it seems thit you too attribute the failure to be due to ammo overpressure.