Is this really an effective measure for overpressure symptoms?

SAAMI says 55,000 PSI is max pressure for .223 and 65,000 PSI is max pressure for a 22-250 (and they both use the same small rifle primer). So if I crater a primer on .223 with 53,000 PSI, why would the same primer not crater on a 22-250 at 60,000 PSI?

I'm going to guess the primer will flatten under 53,000 psi because there is a smaller amount of powder to ignite in a smaller volume-- which creates a pressure spike in that universe-- whereas the greater volume of powder in a .22-250 takes longer to burn and has the bullet farther down the barrel, which creates a lower spike in pressure which precludes the primer getting flattened. Just a guess. Let's see what some real reloaders say...

A weaker mainspring or a loose or large firing
pin will cause craters. It in not a reliable
pressure indicator. With a given rifle if you
increase loadings until the firing pin is pushed
back that is showing you are a damn fool.
Good luck!

All of my 22-250 brass uses a LR primer. Is the new Lapua SR?

quote:

Originally posted by Not_Infringed:
SAAMI says 55,000 PSI is max pressure for .223 and 65,000 PSI is max pressure for a 22-250 (and they both use the same small rifle primer).

My .223 uses small rifle primers.
My 22-250 uses large rifle primers.

quote:

(and they both use the same small rifle primer).

223 is small my various 22-250 cases are large rifle primers.

DocEd per the Lapua website the load data for their 22-250 case is LR primer.

http://www.lapua.com/fileadmin...emingtonCase2010.pdf

OK I just assumed that 22-250 used SR primers. Ooops! I was just looking for an example.

But the concept remains, the same primer is used on a variety of cartridges and therefor maximum pressures. So then is reading a primer for pressure signs worthless?

Thanks,
~Dan

A lot of things effect the primer crater not just pressure. As sated the tension of the spring and the gap around the firing pin have a huge effect. All of the things we watch as potential indicators are just that indicators. To me it's more how they change as I work up the load.

In a given chamber with soft brass large firing pin gap weak spring you might see cratering at a low pressure. Hard brass tight chamber tight firing pin you might see no cartering. I've had rifles that would lose the primer and never show cratering.

Anytime you try and take only one item and say it will ALWAYS happen you are asking for the next time to make you a lier.

If you pay attention you will learn the indicators for a given rifle that give you a heads up that your pressures are increasing or about to get dangerous.

As Paul stated above, primer cratering and flattening may be an indication of high (not necessarily excessive) pressure or it may be something else. Usually as pressure rises you will see primers beginning to flatten and may or may not see cratering or pierced primers. Next you will probably see loose primers and brass flow and you are playing with fire at that point. Bottom line, the only way to accurately measure pressure is in a lab. If you want bullets to go faster than the loads in the book, buy something with larger case capacity.

There is a sequence; The primer pushes the case forward and pushes itself back. If there is
headspace the primer will protrude. If pressure is low (40 kpsi or so) that's all that happens.
If the pressure is higher the case will push back over the now somewhat flattened priber.
If there is headspace the primer will have bulged so that when the case comes back the primer has a "riveted" look.
Good Luck!

As we work up from the starting load, we view the primers for signs of change. This is only 1 of the ways to check/watch for pressure signs. As the pressure increases with the increased powder added, the rounded edge will be gone. Next the primer will flow into the firing pin hole. Reading the primer is very useful. Do a search on "bolt thrust". Different calibers put more pressure on the bolt face then others.Depends on how the brass grabs the chamber wall on firing .Peak chamber pressure in PSI and the inside area of the case head that the gas pressure can work on have an effect. Scroll down to bolt thrust here. Lilja Precision Rifles

From below link. "Most recently I've seen the formula for bolt thrust expressed as being equal to the area of the smallest interior surface of the case web perpendicular to the bore, multiplied by the chamber pressure, and expressed as p.s.i1. This is similar to determining the compression strength of a column by calculating at the smallest diameter, but I don't believe this can be expressed as p.s.i because bolt thrust is suppose to be an aggregate pressure exerted over an area, the surface area at the case web perpendicular to the bore. As a relative indicator it works pretty well. I arrived at a radius by dividing the interior case diameter by two, I squared the result and multiplied by 3.14 to get the surface area. I multiplied the area by the case pressure and expressed the result as pounds of breech face pressure. In any event, the following table represents some relative measurement across several of the chambers available for this gun." Some things I don't know about bolt thrust....

No it is not is the short answer---many variables here but my rifles in most cases would freeze the action or worse before a primer was cratered because of the size of the diameter/length of the firing pin and corresponding hole being bushed.

Anyone who tells you that it is going to have a very bad experience someday because of their ignorance.