stubbicatt
Member
I think the flash hole has been covered. One thing I noticed years ago but which didn't really register at the time, but much later, a primer pocket uniformer which cuts the bottoms of the pockets square can be a helpful indication of excess pressure. Uniform the pockets on all of your brass before beginning this experiment.
If you try this sometime: shoot starting load pressure level cartridges the same day as maximum safe-for-YOUR-gun cartridges in 308 pressure-level bottleneck cartridges, and then de-cap them, run the primer pocket uniformer in there, chances are you will get a "deeper" cut with the higher pressure cartridges. Of course it isn't actually "deeper", as the tool "headspaces" on the case head. Maybe better said, you will have greater resistance to cutting, or more shavings, from the higher pressure cartridges, from what I believe to be a comparatively thin part of the case, the bottom of the powder chamber thru which the flash hole is punched. It is my belief that the brass sort of bows outwards into the primer pocket if pressures are high.
Like I said, it was only after some thinking on what I experienced that it dawned on me that this method is another intuitive way for gaging high pressures. I do not purport to understand it exactly, and I've never cut and weighed brass shavings to get some sort of interpolation, but it *may* be a sign that you have over pressured your brass, so you can back down a bit on the powder charge, vary bullet seating depth, etc.
Same thing with the sort of screwdriver Lee primer pocket cleaning tool. If it leaves a ring of carbon around the bottom of the primer pocket where the edges meet up, it is indicative of "bowing" or a convex primer pocket bottom. --I presume to think that if you uniform the pockets more than some unknown number of times you would be further thinning the brass around the annulus of the flash hole, which might not be such a good idea with 60k psi working on it.
Just an observation.
YMMV.
If you try this sometime: shoot starting load pressure level cartridges the same day as maximum safe-for-YOUR-gun cartridges in 308 pressure-level bottleneck cartridges, and then de-cap them, run the primer pocket uniformer in there, chances are you will get a "deeper" cut with the higher pressure cartridges. Of course it isn't actually "deeper", as the tool "headspaces" on the case head. Maybe better said, you will have greater resistance to cutting, or more shavings, from the higher pressure cartridges, from what I believe to be a comparatively thin part of the case, the bottom of the powder chamber thru which the flash hole is punched. It is my belief that the brass sort of bows outwards into the primer pocket if pressures are high.
Like I said, it was only after some thinking on what I experienced that it dawned on me that this method is another intuitive way for gaging high pressures. I do not purport to understand it exactly, and I've never cut and weighed brass shavings to get some sort of interpolation, but it *may* be a sign that you have over pressured your brass, so you can back down a bit on the powder charge, vary bullet seating depth, etc.
Same thing with the sort of screwdriver Lee primer pocket cleaning tool. If it leaves a ring of carbon around the bottom of the primer pocket where the edges meet up, it is indicative of "bowing" or a convex primer pocket bottom. --I presume to think that if you uniform the pockets more than some unknown number of times you would be further thinning the brass around the annulus of the flash hole, which might not be such a good idea with 60k psi working on it.
Just an observation.
YMMV.
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