The change in chamber pressure with primer change is due to the powder sensitivity to faster ignition from a hotter primer, not from the primer's addition to the powder gas. Nitro powder burn rate increases dramatically with increasing pressure. A "hot" primer gets the powder going faster which ups chamber pressure initially which ups powder burn rate.
Lacking data, I doubt that a stray primer in the powder would burst a barrel. Does anyone have actual pressure barrel data?
I don't think it's as simple and straightforward as a "hot" primer versus a "cool" primer. I don't believe you can isolate the primer variable from the powder variable. There are interactions between the two that are not intuitive. Such as substituting a R209 for a W209 in one recipe and seeing a major decrease in pressure...make that same substitution with a different powder and see a comparable
increase in pressure.
Tough for me to understand how a primer which, unlike smokeless powder, is an explosive, would not contribute to chamber pressure.
Lacking data, I don't doubt
anything.
