Is there a typical order in which the signs of high pressure loads will show themselves? Just trying to figure what comes first, second, third, etc. as pressure rises.
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Is there a typical order in which the signs of high pressure loads will show themselves? Just trying to figure what comes first, second, third, etc. as pressure rises.
The couple of times I saw it, it seemed to start with primers getting more flat at the perimeter and the firing pin hole starting to show some imprint on the primer. Keep in mind though that loose primers can contribute somewhat to that also.
Hoot
From my experience, it's a harder than normal bolt lift. (on a Savage action)
I'll start to get a sharp edge on the primer where the firing pin hits.
Next would be a scar on the case head from the bolt face.
After that would be loose primer pockets. The brass would be junk.
The thing I've run into is I can take a load, say 30 grains with the bullet seated .010 to .015 "off" the lands and I'll get a stiffer than usual bolt lift.
That same load with the bullet seated .010 to .015 "into" the lands and the pressure signs will go away. I can load hotter till I finally get the pressure signs back. Something to do with how the pressure spike forms in the case.
Primer flattening and cratering around the firing pin strike are what I look for have been led to believe that some cratering can be caused by a large firing pin hole in the bolt face. I f you are really concerned get a micrometer and mic the round before and after firing right at the web if it is larger after firing you are getting hot and your brass will soon have a loose primer pocket
If you don't make a habit of loading "hot", you may never see any signs of overpressure. You don't have to be "fast" or "hot" to be "accurate"! ;)
I would say that at first you would see the primers getting flat, then cratering with a small amount pushed up into the firing pin hole, then a ejector mark on the back of the case, then a hard bolt lift, after that would be loose or blown out primers.
+1 with what 82boy said.
+ 1 + --- All good advice - BUT - none of this is concrete. Sometimes you could get just one sign, ( depending on primers, barrel, throat, amb. temp. etc,,) . Like they said above, get a mic., some good books with no distractions. Have had extractor marks with no other clues. My experience shows that the first shot through a clean barrel "IS NO INDICATOR" of what is to follow. Usually have less speed and fewer pressure signs. gook luck
As above you might see one before the other.
Flattened primers, but then again I bought some factory ammo that flattened the primers
more than I would load them. Along with that Cratering.
and hard bolt lift.
Actually hard bolt lift is the first thing that causes me to take a really close look at everything.
Brass flow is a real good one. Swipe marks if you have an automatic.
Case head expansion is another solid indicator.
Primer peircing, its too late and or
Case head separation, close to disaster.
When I got my M12 in .223, I tried the Federal Gold Medal 69 grain load. This was the first time I saw cratering on the primers, and it's a factory load, not an overload. Velocity was measured at 2927fps at 10 feet (26" barrel), temp was hot. Advertised velocity on the box was 3000fps. So yes, a loose firing pin hole can produce this effect at normal pressures. That velocity also tells me the load was not an extreme pressure one.Quote:
Originally Posted by pphreed1