"pressure signs"

R

reynolds357

New member
I am officially done with brass voodoo. I have seriously doubted its safety and merits for many years. Tonight confirmed my suspicions. Due to an error (me being too stubborn to put my glasses on) I grossly overcharged a .25-06 charge. By any data, it was WAY over max. Not a pressure sign to be seen.
 
Back in the late 1980s one of the gun magazines (Jim Carmichael in G&A IIRC) did an article on reading pressure signs. He compared micrometer measurements of brass alongside piezo pressure transducer readings. Most brass did not show high pressure signs until it was in the 68K-72K psi zone, way too high for safe reloading. After that I really toned down my hot-rod loads and stick to published loads. Safer.

People have also gone back and checked PO Ackley's reccomended loads and the old Speer loading manuals and found them to be way high, but reading brass said that they were OK:eek:.
 
There is a very complete chapter in my old 1952 version of “complete reloaders guide” by Sharpe that simply proves conclusively with photos of brass and primers that by the time you can tell from the brass or primer, pressures are far (way far, crazy too high) beyond what anyone would consider safe.

Although much of that “old time” stuff is charmingly obsolete and the technology of measuring pressure has gone from a factory laboratory only affair to a more accurate test device anyone could own... the principles are still shown in a rigorous scientific way, and the basic principles are still the same.

After experimenting lots and not blowing myself up, my new hobby has been “how light and comfortable can I make my loads for the job at hand.”

Glad nothing terrible happened.
 
I look at it like this:

Beyond any published max load = Pressure sign

Velocity exceeding expectations=Pressure sign. Influenced by barrel length.

Those are based on the data of manufacturers who have far better resources than I do.
That is policy I can pass on to someone else with confidence.

However,I still use "seat of the pants" observations for "Yellow light" or a "red light".
I think your point s to NOT use the brass reading voodoo for a "green light"

Examples: Hard bolt lift

Brass extrusion into ejector or other bolt face feature

Primer extrusion or cratering .

Recoil and report that says "Wow,thats zippy"

Again,any of those say "Something is not right" It does NOT follow that an absence of those indicators means everything s OK.

Another direction some folks venture is trying to apply brass pressure sign voodoo to their trusty old lever action,revolver,Krag,Rolling Block,etc.

These firearms are good for 20,000 to 40,000 PSI,roughly speaking. Trying to apply "voodoo pressure signs" that may show up at 70,000 psi to a toggle locking 1873 Winchester is a bit like applying interstate hiway speed limits to
stagecoach with oak axles and wheels.

The "pressure sign" might be the bolt protruding from your cheekbone.
 
Scorch said:
Back in the late 1980s one of the gun magazines (Jim Carmichael in G&A IIRC) did an article on reading pressure signs. He compared micrometer measurements of brass alongside piezo pressure transducer readings. Most brass did not show high pressure signs until it was in the 68K-72K psi zone, way too high for safe reloading.
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Very interesting, indeed. Several SAAMI maximum rifle specs are over 69,000 psi

Especially when the 7.62 NATO proof loads I've shot had peak pressures in the 80,000 to 82,000 psi range. No traditionally popular pressure signs.

There are no established standards for visible or case measuring methods to determine pressure.

Just 1,234,567 opinions.
 
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Here's a bit of food for thought--yesterday I tried Hodgdon's recommended 350 L loads for 350 legend using 170 gr interlocks and lil gun. My first group was a bit above their lowest charge weight. First shot came screaming out of the barrel at 2480 fps. according to labradar. I thought it had to be a fluke--second one topped 2500 fps and primer parted company with the case. That's all the convincing I needed, when I got home quick load told me I was likely up into 80,000 psi land.
 
Scorch said:
Back in the late 1980s one of the gun magazines (Jim Carmichael in G&A IIRC) did an article on reading pressure signs. He compared micrometer measurements of brass alongside piezo pressure transducer readings. Most brass did not show high pressure signs until it was in the 68K-72K psi zone, way too high for safe reloading. After that I really toned down my hot-rod loads and stick to published loads. Safer.

People have also gone back and checked PO Ackley's reccomended loads and the old Speer loading manuals and found them to be way high, but reading brass said that they were OK:eek:.
Click to expand...
I remember reading that ...took his words to heart .
By the time you see "signs" you over the line .
Gary
 
This is a good thread to read. Probably a lot more reloaders should read it.
How often we read comments like “i loaded them pretty hot. They were OK; there were no pressure signs.”
“By the time you see the signs, you are over the line.” Yes.
 
In olden days, Speer said that at ONE "pressure sign" of cratered primer, extractor smear, or hard bolt lift, one should reduce the load by 6%.
Most of the guys thought it was a major concession to "back off" half a grain from a clearly excessive load.
 
Jim Watson said:
In olden days, Speer said that at ONE "pressure sign" of cratered primer, extractor smear, or hard bolt lift, one should reduce the load by 6%.
Most of the guys thought it was a major concession to "back off" half a grain from a clearly excessive load.
Click to expand...
Some reloaders for some mysterious reason push the envelope on everything. One guy I shoot with uses max load for starting load and does not even own any non magnum rifle primers. Everything gets a magnum primer
personally, If I want .30-06 performance, I will shoot a 06 instead of trying to turn my .308 Winchester into one. And so on and so on.
 
Cratered primers on a normal bolthead maybe, but I have two ole mauser customs that the bolthead are somewhat sloppy and let the primer creep back into firingpin hole, one needs a little higher lb spring and that should be better but one is patheticand I knew in the beginning it would do this, so I got my eye out for a better one.
No loads show flattened primers or brass flow.
 
In olden days, Speer said that at ONE "pressure sign" of cratered primer, extractor smear, or hard bolt lift, one should reduce the load by 6%.
Click to expand...
True, but many reloaders don't even know what a crateered or flattened primer or ejector extrusion looks like and will argue with you that their loads are safe. I've seen it on this forum, too. A reloader will post pictures of flattened primers and then argue with people who tell him to back off on his load. Like "if I wanted an argument I would have talked with the guys who already told me it was too hot"! :rolleyes:
 
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