As we all know how dangerous reloading can be in the hands of a nimrod , i just thought I should bring this to everyones attention. An independant test was done with two of the same calibre weapons deriving from the same country , two indentical loads fired in each.....
The result :
Rifle one produced 500 fps more with the exact same load than rifle two , this converts to 20 000 psi pressure . Now you can see why it is so crucial to work up from the bottom ( Might just save someones stupid head )

Just some food for thought.

Regards
Rudie Potgieter

Yeah, maybe . . . if the load data is not drastically reduced to begin with. Most load data in modern publications is substantially reduced, AND the pressure spec for SAAMI is about 5x below the threshold of any sort of catastrophic failure.

Let's get this straight:

I'm not advocating that you crank up the volume on new loads. What I'm saying is that you're no where near the fence line to begin with.

How long do you think component manufactures would be in business if they published data that set you out on the edge of the safety margin?

Published data and SAAMI specs take into consideration variables such as two rifles producing varying pressures/velocities.

I'm betting the higher velocity rifle in this test still performed well within SAAMI spec.

-- dollars to doughnuts.

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.223 Ackley Improved Wildcat Forum:
http://www.hotboards.com/plus/plus.mirage?who=223ackleyimproved

Rudie,

What was the outcome attributable to? When it is stated that two identical loads were enacted and experience dissimilar results, then everything must not have been equal.

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Best regards,
Alex

Democracy is two wolves and a lamb voting on what to have for lunch.
Liberty is a well-armed lamb contesting the vote! - Benjamin Franklin 1759

Alex.

I just went back to make sure I have it all correct. And I Quote a piece from the test result. "These produced a velocity difference , with the same ammunition , of 500 Ft/p/s or 20 000 psi pressure.

Unfortunately I can not vouch for this as I was not present at the test , but this test was done by the Sonchem ballistic proof range. Ah well who will ever know I just thought it might be a good topic for all the beginners & old hands alike.

Good shooting,
Rudie

Rudie,
I don't doubt it, if one had a very tight barrel and chamber and the other had a very sloppy barrel and chamber...I'm sure Sonchem knows what they are doing.

I have seen up to 200 FPS difference from one barrel to another of the same make..I have seen one rifle take as many as 8grs. more powder than another in one instance and many times 3 or so grs. difference with all things equal..

Rifles have a personality of their own and you had damn well respect that.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

Rudie I agree;start the topic,it will be interesting and informative...

This is why you don't know the velocity of a load until it is chronographed.The published charts can be very inacurrate.

Well for one thing, the difference between a fast fast barrel and a slow slow barrel can be as much as 300 FPS. I'll bet a lot of it has to do more with the barrel speeds then the pressures.

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AlleninAlaska

If two rifles produced this much difference in pressure and velocity with the same load, they would produce the same margin of difference with ANY load used in them, even factory ammo, because the difference is due to something bizarre about at least one of the guns themselves.... I don't believe there is any information here that is of use to reloaders at all. (Unless they are NIMRODS)!!

There is definitely some mis-information. The SAAMI specs are NOT 5X below a catastrophic level. Gun manufacturers allow a factor of safety of between 2 and 2.5 times the maximum average chamber pressure of the design load, which is never more than 65,000 psi in the hottest cartridge made, often much less than that. So, 20,000 psi is a very large pressure spike, even if the maximum permissible chamber pressure is 65 ksi. If you perform the calculations for the yield stress in a gun barrel you will find to your shock and horror that the apparent factor of safety is about 1.2! And this does not take into consideration the stress multiplying effects of the threads on the chamber. The steel is stronger in dynamic loading than the static yield stress would suggest, but what that figure is or exactly what factor of safety is applied I could not get Ruger or Remington to divulge when I discussed barrel design with them some years ago while working on a lightweight gun barrel design project for an anti-materiel rifle. If you want to know the truth call up H.P. White Laboratories or SAAMI and ask them about the limits and the design rules for barrels. The margin is not as large as some think.

I saw a video of HP labs testing a FAL, the load produced over 250,000 psi, didn't do much damage, barrel and receiver were still intact, blew magazine out, extractor, etc.

Sorry Guys

I have been away this week & only caught up on the threads when I got home . The only reason thought I would start the thread is for the simple reason that we all know there are too many daredevils in the reloading rooms . Say what you may but I think that Eldeguello has got the right attitude , that there are some " Nimrods" out there . With all due respect to old hands at reloading who knows quite safely where to push the limits to . BUT there are also beginners that try to push every last fps out of their .22 lr if they could , I think you get my drift of where I am going with this. There have been blow ups and it is for the simple reason of carelesness. So all I am saying is be carefull no matter what the book says .

How do we know this converts to a 20,000 PSI difference? Do we have a piezo strain guage? And, while 500 FPS is WAY more than I have ever heard of or experienced, each could have been safe in the rifle it was fired from...Maybe not. Theoreticly, if one rifle had an erroded throat and worn riflings, it might give substancially higher velocity(though accuracy would be terrible). Some newer rifles suffer lower velocities because the barrel hasn't been polished from firing many rounds-very small burrs. Kinda like an old Hemi engine; they ran slop-@$$ loose but made more power than their competitors because of reduced friction. I am not saying this is the case, just a possibility. And for that matter, the chronograph could have played it's tricks too.

With a .30-378 WBY factory rounds I have ejector mark on all of them,180 Barnes X,chrono 3356 f/sec.When reloading getting that high ,I have pressure signs,primer pocket enlarged,hard bolt lifting,the cases are ruined;but with the Norma ammunition,I have no pressure signs,every rifle is particular but having ejector mark with factory loads,there is a missing link somewhere;well made chamber may be ,but I think something is not quite right...

Sniper06

I think you do have a good point about the chronograph, it could have been heat, muzzle blast who knows . But I do think this is a good reading on the pressure side as this is a ballistic proof range the test or .... I was just pondering it could have been a hoax , hell I wouldnt know myself :-)