Have any of you ever had your reloads pressure tested by a recognized lab? I asked the French lab in St. Etienne how much it would cost to pressure test 10 rounds of 404 Jeffery and 10 rounds of 416 Rigby. The answer is they send them to Birmingham England and want around $300 to do it.

Actually that isn't a bad deal. H. P. White labs charges $275 for CUP tests and $475 for piezo (don't know why the difference, evidently the CUP equipment is paid for and the piezo isn't And they also do 10 rounds.

Mike,

If you have already pressure tested your bullets in the two calibers I mention with Vihta N150 then you can save me some money. I was going to load some of your bullets (except for the now very rare SS in .423!) and get them tested just to know where I am.

quote:

Originally posted by Wink:
Mike,

If you have already pressure tested your bullets in the two calibers I mention (with Vihta N150 for the 404 and N165 for the 416) then you can save me some money. I was going to load some of your bullets (except for the now very rare SS in .423!) and get them tested just to know where I am.

Corrected.

Hey Wink, for that kind of money, you can buy your own pressure testig setup.
http://shootingsoftware.com/Merchant2/merchant.mvc?Scre...TGY&Category_Code=PT
It's probably not as accurate as lab testing but from the articles I've read, it's pretty close.

Fred,
That looks interesting. Are there any reviews I can read to learn more about this software?

quote:

Originally posted by Wink:
Have any of you ever had your reloads pressure tested by a recognized lab? I asked the French lab in St. Etienne how much it would cost to pressure test 10 rounds of 404 Jeffery and 10 rounds of 416 Rigby. The answer is they send them to Birmingham England and want around $300 to do it.

Really cheap compared to the CIP agreement fees I paid for the two cartridges I developed and produced for a Ministry of Interior service in 2003..

I am interested in the homemade pressure testing software too. I don't really understand how to get this working accurately without a reference round with known pressure.

The pressure trace equipment works pretty well, if measurements are correct, etc. If you're not capable of that, you shouldn't attempt it. Edmond- the problem with pressure testing is- what did the others set their equipment with? It is not like a set of scales where you can set a check weight on it, and even if you could, what did they weigh the check weight on? As you can see, calibrating pressure testing equipment is a never ending chain of questions. The pressure trace is the best thing we have for checking pressure and is certainly sufficiently accurate for our use. After all, what we are wanting to know is not whether the pressure is 60420 psi or 61000 psi, but whether it is 60000 psi or 71000 psi. You can also believe that the mechanical symptoms of high pressure such as hard extraction, brass flow into the ejector cut, etc. won't happen until over 70000 psi in my experience. I've had some perfectly normal shooting loads I'd used in 100 degree heat for years with no problems, but were a little over max by some books, but were normally functioning loads and shot well. The pressure was in the vicinity of 67-68000 psi. I think however it would be worth the $300-$400 to send some ammo in and find out just how close your home pressure testing equipment is. My bet is that it's plenty accurate for home reloading use.

I know only the basics in this field and that everything is set with reference to the crusher method, including the piezo electric system.
I'll try to find more about the system proposed here.

Hi Wink, Edmond,

Send me a PM and I can direct you to the complete C.I.P. protocol, dimensions, pressures and testing methods.

I can also describe why the labs need ten rounds and the conundrum about chasing the absolute reference to determine pressure exactly.

I will also send you some links to full information about the two readily available strain gauge systems.

lawndart

PS the C.I.P. source CD contains all information, graphs, instructions, etc. in francais, english and Bosch.

quote:

Originally posted by Edmond:
...I am interested in the homemade pressure testing software too. I don't really understand how to get this working accurately without a reference round with known pressure.

Your observation is absolutely correct - it can not be done without a known Standard. Anyone thinking otherwise simply does not understand the entire problem.

Whenever you see someone post that they "know" a Load is xxKpsi and they are using an Non-Calibrated HSGS, it should be an immediate indicator that they don't know what they are talking about.

Best of luck to you folks.

I am going to assume that factory loads are pressure tested, this would seem to be obvious so correct me if I am wrong. If you know the factory load pressure (some manufacturers will give you this information), you can then calibrate your pressure testing software. Am I right?

This is an honest quetion; If we have a known Std. or ammo that is pressure tested and published, Is the related pressure an average in many chambers or just the one it was tested in? In the interest of accurate numbers would using either in one's own chamber be meaningful? roger

There is no such thing as a round of ammo that is guaranteed to give a specific pressure when fired.

Anyone who claims the existence of such ammo has never fired "reference" ammo in several different barrels, even if all the barrels are "identical".

KenO

quote:

Originally posted by Wink:
... If you know the factory load pressure (some manufacturers will give you this information), you can then calibrate your pressure testing software. Am I right?

quote:

Originally posted by Dr. Oehler:
... There is no such thing as a round of ammo that is guaranteed to give a specific pressure when fired.

Anyone who claims the existence of such ammo has never fired "reference" ammo in several different barrels, even if all the barrels are "identical".

I agree with both of the above posts.

I agree with Dr. Oehler that you can not count on a "specific pressure", there should be an "Average Pressure and Range for the Lot". I also agree that there is little chance the Pressure Guesstimates from a HSGS fiasco will be the same as the Reference or Calibration Ammo.
-----

Hey Wink, If you get a company to give you their Pressure Data, it will not be xxKpsi. What they should give you is something to the effect, "That Lot of cartridges has an Average Pressure of xxKpsi with a Range of +/- yKpsi as Tested on our equipment." If they do not give you that information, then it is questionable as to it's value.

Lets say they said that the Cartridge in question has a SAAMI Spec of 58Kpsi. And the information you got from the Cartridge manufacturer stated that specific Lot Tested 52Kpsi +/- 3Kpsi. You take the 20 rounds of ammo and fire it through your rifle, with the Non-Calibrated HSGS fiasco, and determine the Average Pressure Guesstimate is 59Kpsi +/- 2Kpsi.

That does not mean you "necessarily" have a problem, it may only indicate, when the HSGS fiasco was set-up, that some or all of the Guessing at Chamber Dimensions, Fudge Factors and Strain Gauge Application are just hosed-up a bit. Your HSGS fiasco is off by approximately 7kpsi +/- ?Kpsi. But, when you Develop Loads, you should use the 7Kpsi Off-Set and STOP when the HSGS fiasco indicates an Average 59Kpsi. If the Range is wide, then you need to back down from 59Kpsi or use a different Primer/Case/Powder/Bullet combination.

It could also be because you are blessed with tight Chamber/Bore dimentions, the HSGS fiasco was set-up correctly , and that you are just seeing the Off-Set for that Ammo in your specific rifle.
-----

This next possibility is the part that grinds on me.

The HSGS fiasco reading could just as easily go the other way, which is potentially w-a-y more dangerous, because the people who buy the HSGS fiascos, and who think they are infallible, could have gotten an Average Pressure Guesstimate of say 48Kpsi +/- 4Kpsi(with the previously mentioned Reference Ammo) and decide to just keep dumping in the Powder. Seriously BAD WRONG!

But in any case, you still want to watch for All Pressure Indicators, not just the HSGS fiasco Pressure Guesstimates.

Best of luck to you.

What worries me more with the DIY system is that the sensor is installed on the outside of the chamber and records the temporary deformation.
Can't be as when a known material is crushed by the gas pressure taken directly from the ammo being fired or a system based on reference to this principle.
Won't a sensor record a different value on say a Remington or a Winchester chambered in same caliber?

quote:

Originally posted by Edmond:
What worries me more with the DIY system is that the sensor is installed on the outside of the chamber and records the temporary deformation.
Can't be as when a known material is crushed by the gas pressure taken directly from the ammo being fired or a system based on reference to this principle.
Won't a sensor record a different value on say a Remington or a Winchester chambered in same caliber?

No, as long as the ID and OD chamber measurements under the gauge are accurate. Young's Modulus does not differ significantly amongst common rifle barrel steels.

Just because so-called "reference ammo" or an ammo manufacturer's lot is specified as "52Kpsi +/- 3Kpsi" does not mean that it will generate that pressure in any other rifle than that which conforms to the reference or manufacturer's test rifle. Tell me where one can even purchase "reference" or "calibration" ammunition? It is well documented in the literature that ballistic strain gauges are a useful tool that provide accurate results within their operating margin of error.

quote:

Originally posted by KenOehler:
There is no such thing as a round of ammo that is guaranteed to give a specific pressure when fired.

Anyone who claims the existence of such ammo has never fired "reference" ammo in several different barrels, even if all the barrels are "identical".KenO

Thanks ,Ken I enjoy your chronograph. roger

Wink, that price--$150 for each set--isn't too bad. If you're in France, you might try cutting out the middle man and contact Birmingham directly.

In the U.S., Western Powders used to advertise they would test handloads in their piezo barrels. They haven't advertised this service recently, though, and I don't think they have either 404 or 416 barrels anyway.

NFMike, I too was told by White that CUP tests are less expensive. In looking over SAAMI documents, it's not difficult to imagine why this is so. For one thing, CUP tests don't have to calibrate your brass, which is an extra step. With a conformal piezo transducer, the brass is between the gases and the sensor, and so the brass restrains the pressure somewhat. How much it does varies with brass thickness and hardness, and this effect can be tested with a separate, hydraulically pressurized set up. This step also verifies the piezo sensor is still in calibration. Wink's test might not have this calibration step (some standards call for the piezo sensor to be placed just in front of the case mouth), but SAAMI standards (which H.P. White would use) are for the conformal set up. With the crusher, you just start firing cartridges and measuring crushers.

Edmond, strain gauge set-ups are calibrated, but in an indirect manner. The properties of steel and brass are fairly consistent, and if you can make accurate measurements of the thicknesses, you can readily relate strain to pressure. The strain gauge is calibrated by its maker, and the sensing electronics can be calibrated with a resistor.

Each of the steps just described has some margin for error, and all such errors in all the steps together can conceivably compound unfavorably. If you have a standardized chambering and if your barrel is in good shape inside, you can use factory ammo to establish an "indicated" psi from the strain gauge that should be safe for handloads in your gun. It may not be a SAAMI max load, but safety is more important than the last few fps.

quote:

Each of the steps just described has some margin for error, and all such errors in all the steps together can conceivably compound unfavorably. If you have a standardized chambering and if your barrel is in good shape inside, you can use factory ammo to establish an "indicated" psi from the strain gauge that should be safe for handloads in your gun. It may not be a SAAMI max load, but safety is more important than the last few fps.

Very true.
There are stack errors anytime more then one measurment is needed to set up any type equipment. The amount is hopefully held low enough to give a good idea with the pressure trace of where we are if we measure properly.

The factory ammo is a good source for a "base line" to stay with when useing a pressure trace unit. The ammo is loaded by the factory to be close to the SAAMI established max. We don`t need to know the exact pressure it gives in our rifle as it will almost certainly not be as high as in a SAAMI min chamber/bore test bed. It is though "max" ammo as far as SAAMI and the manufacture is concerned. We can record the pressure we get with a couple brands of factory stuff and take the highest average as our max and highest recorded as our "max allowed" pressures and be pretty sure if we stay within these as measured by the strain unit we are within safe pressures at a level very near industry max.

Originally posted by KenOehler:
There is no such thing as a round of ammo that is guaranteed to give a specific pressure when fired- This is very true, as chambers, barrels will be different. Therefore, just because you send your ammo to someone and have them test it in another chamber it is somewhat meaningless. A pressure trace isn't perfect but is far and away the best we have available for home use.

We have Ballistic Research testing 12ga 3"
plastic case loads. Uses transducer.I will
down the road send him barrels chambered
for our long 12GA FH case and my 700HE.
He will thread them for his reciever
and drill them for transducer. He will
drill cases to match transducer and after testing a batch, sends drilled cases back
for me to reload for next test needed.ED

jstevens, I wouldn't say it's meaningless, because care is taken to keep the dimensions in a pressure barrel to minimums. If your sporter has been cut to allowable dimensions and if you've kept it well maintained, your pressures will very likely be below that in the pressure barrel. There are, as always, several "ifs" in this line of reasoning...