Has anyone ever done a test to see what the actual pressures are when accepted signs eg flattened primers, sticky bolt etc start to appear.

Are the signs too late eg you see them you're allready dangerous?

Are they greatly affected by other factors eg different makes of primer (rem91/2 vs others) headspace etc to the extent that they are unreliable.

Am I being paranoid?

As you can tell I have a bit of a thing about this - I just wonder how well what may be seat of the pants sits (ha ha) with the proximity of these sorts of pressures 6" from the face unless it's proven to be pretty much infallible.

1894,

John Ricks has the M43 Oehler with pressure transducers. I'm working from memory, but I believe he told me that you were usually hitting about 70,000 PSI before most people could see pressure signs. Accepted max pressure for modern bolt rifles is usually no more than 62,300 PSI, so you're about 12% over listed max.

Some rounds, like the Rigby have maxes at 51,000 PSI, so you're way over when you see signs.

The best indicator I've found is before and after measurement at the cartridge base. When it swells a measurable .001 you should stop and back up a little.

Hopefully we'll get other opinions and methods, too. Maybe John will correct my memory.

Don

1894, Don is correct by the time you start to see pressure signs in most rifles you are well beyond max.pressures. If you don't have pressure measuring equipment another way of judging pressure is the use of a chronograph. If the max. velocity of a cartridge is 2400 fps. with a certain powder and bullet combination and you are getting 2500+ fps. more than likely you are exceeding max. pressures. You can't have abnormally high velocitys without abnornally high pressures, pressure and velocity go hand in hand.

1894:

Ditto Mitch. All things being equal, a chrono is a very good gage of pressure in a SAMMI spec chamber. Most modern factory rifles should follow the curve very well. If you are 100fps over max velocities and you see very flattened primers, you are beyond max pressure.

When you step into wild cats, monitoring pressure becomes more critical. Alterations in shoulder angles, can cause pressures to rise. In addition, you may not be able to find a lot of reloading experience with a wild cat. You may find yourself pioneering the pressure curve.

In regards to older guns, you can be well within the pressure norms for modern guns and experience a chamber or barrel failure. This is due to weaker metals and fatigue.

In short, if you are shooting a modern gun and are within max velocity, I would not worry. If you are shooting a wild cat or someone else�s creation, go find a competent gunsmith and have the chamber measured, action inspected, etc.

However, if you are really interested in pressures, go get an Oehler M43 like Don G mentioned. The only problem is you will need to remove the blueing on your gun to mount the strain gage. (Not something that I want to do with a fine gun). Otherwise, clean your gun, keep it in good condition, reload at or below max loads, monitor your brass, and you will never need to worry too much about pressure.

Shooting guns is an inherently dangerous activity. I see too many people just blazing away with no thought or consideration of what they are doing. Always exercise caution and common sense and you will fine....

Z

I am 53 and started realoding at about age 16.

I am amazed that I am still here.

Mike

About 10 yrs ago I started playing with the 6MM Rem A good friend and experienced loader told me 48gr IMR4350 with 75grhp was the way to go. I tried it and it was great. Then about a year later ,relying on memory , I loaded with an 85 gr hp. It was a good hot load and accurate too. The only problem was the primers fell out when the cases came out. The primers were not flat but the primer pockets sure wouldn't hold a primer in anymore. So much for flattened primers.
Pressure transducers are the only way to go.
Years ago when I was drag racing you could always tell just before an engine let go . When you saw a super run you could bet on the next pass the engine would quit out the bottom. There was no friction 'cause there were no bearings left. Same with primer pockets.

Very chastening to hear. My route has allways been to not go nearer than a grain of published max (in 50-60gr loads) loads and preferably keep it 2gr less. My concern re the velocity/pressure curve is that the published velocities are just so dammned variable! The difference between vihtavuori and Nosler velocities using same powders and bullets is of the order of 150fps!

Anyhow I wanted 2800fps with N160 and 120gr ballistic tips in my 6.5x55 and got 2850 from 45gr. Seems I must have a tight chamber/barrel. Is there anyway of telling whereabouts I'm at pressure wise?

1894,

QuickLoad says there was a "fast lot" of N160. You must have some of it. For the fast lot in a 24 inch barrel QL says 45 gr == 2817 fps at 47,400 PSI. Max for the case is 55,000 so you should be fine.

Don

Don,

Many thanks for your help, this forum really is the business. Dare I ask?

Do you have lot numbers for this fast powder

Is 55,000psi the SAAMI or for want of a better phrase +P (I only know the SAAMI limit in CUP)

Hey 1894, I've not seen anyone mention using Pressure Ring Expansion as a method of knowing when to stop adding Powder. This is a bit different than Case Head Expansion.

You do need a box of factory ammo to establish a "Standard" for the amount of Pressure Ring Expansion to consider as MAX.

And you will need 0.0001" capable Micrometers to do the measuring with. A 0.001" capable Caliper is just not accurate enough.

The Elders that taught me Handloading used this method. And I've noticed in Bob Hagel's and Ken Waters' books that they both use Pressure Ring Expansion as one of their regular Handloading procedures.

If you need any more information about this method, I can email you a File on it if you are interested. It works well for me, but it is a bit slower than some other methods. I see that as a good thing since that gives me a bit more time to think about what is happening with the Load and it allows the barrel to cool a little longer between shots.

Anyway, good luck to you as you develop your Loads for the rifle.

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Good hunting and clean 1-shot kills, Hot Core

1894,

The 55000 PSI absolute max is the only limit listed for "6.5x55 Swedish" in QuickLoad. It is consistent with 47000 PSI for the 8mm given the area under pressure, so I think it is "about equivalent" to SAAMI. There is no direct conversion from CUP to PSI.

Don

I agree with previous posters, "pressure signs" are the indication you should say oh shit, not, well I'll back off a 1/2 grain. The chrony matched with solid published data is the most cost effective method of interpolating safe pressures.

Fortunately modern guns have a pretty good factor of safety designed in, not to say you can't dissasemble them by monster overloads, or a stead diet of hot loads. There is a huge caveat that the newly popular larger diameter beltless magnum cases diminish this factor of safety, and some of the modern brass can be loaded to very high pressures before indicating pressure, ie 75, sometimes 80 kpsi.

Simply put, pressure signs were used as a method of interpolating pressure when we simply didn't know better, or have methods of quantifying how crude those methods were. We now know better, and should be more prudent.

Nothing made by man is infallible. One understand the prudence of a new reloader, and applaud you for exhibiting it. Once you get more experience under your belt, you'll have the same confidence setting off your own loads as factory stuff. Just stick to the basics, and don't let your guard down, or get sloppy.

HotCore,
I'm with you. Your the first guy I've heard mention Hagel and Waters pressure ring system. Measuring case head expansion is a complete waste of time. Firstly, they are never round to begin with and secondly, by the time you get a reading you already have primer pocket expansion. I briefly describe my system in the inntroduction to the .505 Gibbs data posted in Reloading Pages of this website. I'll be glad to discuss it via email with interested parties.

Many thanks guys - I'm happy now. The 8x57 SAAMI in CUP is 37,000, the 6.5x55 is 45,000CUP so I'm obviously pretty soft which is what I want, the rifles a beauty and my gunsmith is not getting any younger so the barrel needs to last. Not new to it just crude in some aspects as I'm a sporting rifle shooter first. Getting some unexpected velocity made me think I ought to re-examine some of my assumptions.

PaulH I'm sure you don't mean to but your post sort of reinforces the feeling that only new loaders need to be cautious. You can get on a road to pretty dangerous place if you lose that inate sense of caution and don't pause for thought and re examine every now and again. Also for the record I only fired 2 rounds of federal classic 140gr before I pulled them and used the brass. The primers were so flat you could fry an egg on them!

[This message has been edited by 1894 (edited 05-24-2001).]

Hey Nickudu, I was very fortunate to be reared around some very knowledgeable Handloaders. Pressure Ring Expansion was "The Method" back then, and nothing has come along to beat it yet. From my perspective, Hagel and Waters are as good as it gets when it comes to Handloading knowledge.

That is not to imply that you can't get usable information from the Velocity and Strain Gauges glued to your barrel. I do think a person should use EVERY method he has available to him while Developing Loads. But, use all of them, not just one.

The only real problem I see with the other methods(velocity, strain gauges) is that they do not take into account the actual "case" which is the weakest link in the process.

But as for "my firearms", I'd be as likely to glue a Strain Gauge to one of them as I would to bury it in the sand at the edge of the water during low tide for 3 months.

And I've seen people use "Velocity" as the sole method of determining when to stop dumping in Powder. Of course, they really have no idea at all where the Pressure is. Too many variables from the barrel, cases, primers, powders and bullets that could mislead the person if they use Velocity as the "only" indicator of when to stop.

Same with the Ballistic Software programs. They are excellent for "guidelines", but certainly not something to just "Run the Load" and then go load it up to the "calculated" MAX.

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Good hunting and clean 1-shot kills, Hot Core

Hot Core,
I'm just surprised to finally find someone else who subscribes to this system besides myself and a few of my buddies. We all have a lot of confidence in it and have added our own "stuff" to it, over the years.
I'm glad for Ken Waters and Bob Hagel too ... they deserve recognition.

Best .... Nick

Hello,
Someone mentioned removing the blueing from the gunbarrel. Will the gauges work on a stainless (plain) barrel? Also different brands of primers "flatten" at different pressures so there is really no rule of thumb to compare their physical aspects to the pressure readings.

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Safety & Ethics,Accuracy, Velocity, Energy
Joe M

[This message has been edited by JoeM (edited 05-24-2001).]