Don't know whether you're an AB or a naval aviator, but either way I'd hate to lose you. [I know now; I looked it up in your profile. Still wouldn't want to lose you.] While the above advice was probably a good partial answer to your actual question, I believe that you should be aware of the opinion (knowledge?) passed on by Art Alphin, retired Army Ordnance colonel, in his A-Square reloading manual, available from Sinclair. Basically, he says that ALL of the classic pressure signs are unreliable in that safe pressures may be exceeded before seeing the signs. He recommends using reliable data from loading manuals and not exceeding the velocity in the manual. He doesn't think you should load, at least not rifle cartridges, if you don't own a chronograph. Rather conservative advice, but probably not a bad idea, considering the possible results of an error.

Good luck!

Ricky Recono, formerly of the
World-Famous Pukin' Dogs

[This message has been edited by Recono (edited 12-12-2001).]

The action will be hard to open, or seem sticky when trying to open.

The back of the case may have extra imprints or indents.

The primer pocket will not hold a primer firmly.

These are the things that happened to me, but I also understand with extreme pressure you may split the neck of the case. I do not know if that is true or not.

My recommendation is to back off a grain or two, and study the case again.

Good Load'in,
TGW

quote:

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Originally posted by Multi Vis:
The flattened is generaly the first sign of pressure. When you seat a primer when reloading you will notice that the edges of the primer once seated into the case have a slight rounded edge going into the case. When fired the primer will flatten out with the buildup of pressure,the more pressure the more flattening and filling of the primer pocket will be seen. Flattened primers do not mean over pressure but more like you are getting real close. If you start seeing cratering of the edges of the fireing pin mark on the primer then you are there and should be backing the load off. When using the condition of the primer as a sign of pressure you need to use the same make of primer as different Mfd. of primers use different hardness of primer cups which will read different between makes. Other signs of pressure is a hard bolt lift and extractor marks on the case but like I said the primers will show it first. Regardless of what the primer shows if you get either of the other two signs back the load off.
Go slow and follow your manual and you will see how the primers change with heaver loads.
Lets see - you are in Va.beach and use FA-18 for a handle - bet you be in the Navy and work on them!!!!OOPS - how bout fly them! Grew up in No-poke so know the area well.
Multi Vis.

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Things like setting back your locking lugs are no fun.

Anyway, be safe, behind BOTH triggers, and I appreciate your service. HTH, Dutch.

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Originally posted by fa18hooker:
I've seen numerous passing comments to "check for signs of overpressure" during a load build-up. Specifically,

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I saw lots of repeating of what pressure signs to look for, but would like to point out that 'overpressure' is not an (exact) thing.

Some will mean a particular psi (about 60,000 to 65,000 for many high pressure rifle rounds) that is rated by the factory.

But, a remington 700 in 30-06 is lower than the same action in 300 win mag, which has a larger case. The steel around a .300 win mag should be less capable of holding pressure than the same action chambered in 30-06.

Other actions may not be as strong, but how do we know?

A good example of why caution must be taken in talking of detecting 'overpressure' is the good old 45-70. Reloading manuals list loads at different pressure levels for different actions. It may be the first pressure sign will be the action coming apart, if a high pressure load is fired in a weak action.

Others (OKshooter, Ken Howell) have claimed (and I believe them) that certain brands of brass and primers won't (sometimes) give any sign of overpressure until well beyond the maximum spec pressures. This doesn't mean such pressures are dangerous in that gun, but it doesn't mean they are safe either. How do we know how strong a gun and brass combination are?

I saw someone suggest that proof loads for a 30-06 are in the range of 75,000 psi. Does this mean that is the limit, Or even that that is safe in repeated use? NO!! It is used as evidence that some derated number is safe (maybe 60,000 psi). It doesn't tell us how much is safe or what the failure mode will be.

Some guns (do to poor design, or maybe not) have weak points which can be used to detect over pressure. The case bulging in the brass of a Glock .40S&W. The drag in opening caused by the stretch of the top strap in my ruger hawkeye.

One manual I read suggested that new factory ammo could be fired, then from the same lot, the bullets and powder could be pulled and the load in question substituted. Compareing fired cases might give an indication if pressure was extreme. Such is why the M43 pressure unit is used by some.

Anyway, I got carried away, when I just meant to say that overpressure signs can indicate dangerous loads, but lack of signs should not be viewed as proof of in spec (or safe) loads.

JerryO

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Originally posted by Dr. Duc:
Ken Waters says that all "classical" signs are unreliable. Use the case expansion as measured by a micrometer-.0004" max in a ring in front of the base of the case. Easy to do!

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So what your advocating is expansion of the web of the case- which is unsupported by barrel or action during firing. This does not factor in the variance in case head metalurgy- which does vary from manufacturer. I've observed lot numbers of brass that any web expansion definitely would be excessive pressure.

quote:

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Originally posted by Multi Vis:
The flattened is generaly the first sign of pressure. .... If you start seeing cratering of the edges of the fireing pin mark on the primer then you are there and should be backing the load off. .... Other signs of pressure is a hard bolt lift and extractor marks on the case but like I said the primers will show it first.

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Sorry, but my experience is quite the opposite. Some barnds of primers will flatten easily without excessive pressure, even some factory loads will flatten.

Cratering is much the same. Depending upon the amount of firing pin protrusion, primer hardness, striker pressure, firing pin hole dimension, the primer may crater. I agree that super-excessive cratering is indicative of excessive pressure, but this has to be based on observations over time of various loads. Safe loads in many rifles slightly crater.

While primers are not necessarily indicative of high pressure, hard bolt lift and ejector marks on the fired brass are DEFINTELY signs of high pressure. If a factory loads extracts easily and your handload doesn't, the pressure is too high, for a variety of possible reasons. An ejector mark on the head of the case indicates that the pressue is so high that the brass is flowing into the ejector hole in the breech face. Back off !

fa18hooker: Buy a couple loading manuals and read the instructions which detail this before you start pouring powder into cases.