Originally Posted By: venaticCatShooter that's interesting and I think I will take this opportunity to learn something. If using the two cases say in the video and both were fire formed previously and just neck sized would a primer that looks flattened like the one on the left be a sign of pressure? That would take the excessive head space out of the equation. OR are you saying never pay any attention to the flattening of primers just watch for cratering and sticky bolt and or swipes on cases.
I do agree with John(pcammo) that I watch my properly sized cases and if I am getting 9 or more loadings without the primer pockets loosening then I am OK. I get exactly 9 from my 17 Remington loads OTOH my .221 FB brass lasts forever with what the book says is a max load.
I would guess TC Encore's fall under the springy actions because I have had a couple of issues with brass with them.
That's a good example. Say you have a bunch of cases that were factory loads and shot in your gun. They should have 0.000" to 0.002" headspace (none for practical purposes).
Now you load up a bunch of test loads. As the loads get higher and higher, there is more pressure on the cup of the primer - and it's natural desire is to expand out to fill any space, until it is touching the bolt face, and pocket walls, 100%.
Remember that the primer cup is only 0.020" to 0.025" thick, and the metal is not very hard. So as pressure grows, it starts to loose that "round edge" look, and starts to have a little flat look.
This is normal. As pressure continues to rise, the primer will continue to loose that round look and the flat area will get slightly larger.
Now... as long at the primer is not oozing back into the pin hole, every thing is fine. This just the natural result of the pressure on the insides of the primer.
When the primer cup, just under the pin, starts going back into the hole by pushing the pin back, then you are at the ragged edge. If it continues to push until the part of the cup under the pin, gets forced back into the bolt face... then the case pressure will flow back into the bolt, and that is a very badd thing. That is why there are holes on the sides of bolts (or some other means of letting the gas escape).
Now... at one time (when gun companies only hired guy people to work there), you never had pin holes larger than the pin itself - by maybe 0.001" to 0.002".
But for maybe the last 20 or so years, (due to the CNC machines turning out 1,000,000 parts a second, without individual inspection, some are going to be too large or too small. )...
... Remingtons (and some others) have been coming out with some firing pin holes that are ~10 to 12 thou larger than the pin. This allows the primer to flow back a little - but it does this with almost any pressure - even wimpy factory loads. These "flow craters" look different than true "pressure craters"... they have soft edges and look rounded.
True pressure cratering has sharp outside edges and a straight wall on the outside, and the pin dent looks shallower than normal.
These are the reasons that a beginner should always shoot a few factory loads (preferably Remington or Winchester, but not Federal) - you need to know what a "normal" primer looks like on your rifle.
The weak place in the whole cartridge system is the primer and the firing pin, firing pin hole, and spring. Those are the only things that keep the whole damm thing from coming apart.
In large rifle, all the cups are 0.025" to 0.027".
But in small rifle primers, the Federal, CCI 400, and Rem 6-1/2 are 20 thou, and the Rem 7-1/2, the Win SR, the CCI 450 and BR-4 are all 25 thou... so they can hold 25% to 35% more pressure before cratering (or flatting).
Way back when, people used to think the Fed primer was hotter, because it would crater on loads that would not with Rem 7-1/2, Win SR, and BR-4, etc... but it turned out that it was the wimpy cup on the Federal primer that was the cause of the cratering.
To answer your question more directly... don't worry about flattening, as long as the primer dent looks OK
If this doesn't make sense, tell me and I will try it again.
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Originally Posted By: pahntr760I've seen Federal primers 'crater' and winchester primers, with the same load were fine. Now what do I do?
Stop using Federal primers
Quote: For one I don't shoot the Fed primers in that load anymore. The load doesn't stick the bolt, with either primer. And it's accurate.
So, is a cratered or flat primer ALWAYS a excessive pressure sign??
The Fed primer is thin and soft, which is why it would crater, but there were no other signs - I have 3,000+ Fed SR primers that I have had for maybe 15 yers that I might use in a 22 Hornet or .218 Bee... but I would never use them in a cartridge like a 223.
A flat primer is not a sign of pressure - a VERY flattened primer is a sign of excess head space.
A truly cratered primer is a sign of excess pressure for that primer] - if you have a load that is cratering Federal primers, it might be a 48Kpsia load - but with that primer, it is a shakie load cuz a little more, even though the pressure is not high, the Fed primer can let go into the action - whereas, a Remington 7-1/2 or a CCI BR-4 will hold 55-60Kpsia and not crater, in the same rifle.
The amount of pressure is not a concern of the modern rifle - the modern rifle will not come apart at 100,000 psi - it is the primer - pin - and spring, that are the determining factors. The rifle can take whatever you throw at it.
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