Quote:
Originally Posted by HW223
That is exactly what you don’t want to see , the primer is still round at the outer diameter , but is cratering , this is not a good situation and should be corrected , when it’s right the primer will “ flow “ into the outer radius with and indent in the middle from the pin and zero flow at the pin ,
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The primer flow shown is indicative of an oversized firing pin hole and not indicative of high pressures as you have explained and can be fixed by bushing the hole or replacing the bolt with a custom one. Remingtons are noted for this but the flow is still caused by pressure as that problem will also disappear as pressures drop to Saami pressures just as PRE does.
The primer flow I am measuring is into the firing pin hole at the center of the primer and usually happens afterflow into the outer radius or "flattening". It can be caused by a weak firing pin spring but is most likely caused by the pressure getting to the point that the firing pin is pushed back as pressure builds. I know that my 20 caliber rifles do not have this problem as it does not show up until pressures get well above Saaami Pressures for the 222/223 cases and PRE reaches near max. My 20-223 EXTREME has allowed me to compare results with those on Factory 223 ammunition and they are the same. In all 20 cal rifles that I have done this with, including CZ, Remington and Sako, this flow, would get to about 0.008" before Rem 7 1/2 primers pierce and occasionally they blow as the primer pocket stretches by 0.007" which takes a whole lot of pressure. This will usually happen without the bolt handle seizing with these cartridges although it may get" clicky". I have found this true in other cartridges as well and have only had a problem due to intentionally pushing to the limit to try and find the Max chamber dimension at the datum, in these wildcats, as my measurements keep me in the "safe zone" which is much before the bolt gets stiff .