Aren't you the one who said he'd like the ammo manufacturers to include actual pressure and velocity readings on or in the box with some of their retail ammo? (So we could use it for comparative purposes in setting up/calibrating our instuments.)

I ran into the NRA columnist to whom I forwarded that request, in the grocery store today. He has elected to use your question (Why don't they, that is) in his next column.

I don't know how many months in advance he sends his material in, but I'll find out from him tomorrow or the next day. Will also check to find out which mag it is going to appear in....

BTW, he is going to join AR within the next few days. Will be a pretty valuable addition here, I think.

He is a BATF-certified firearms examiner, whose testimony has resulted in allowing the import of many firearms and parts which BATF would otherwise have not allowed to be imported; a professional "expert witness" in many, many, firearms cases, both civil and criminal, for both plaintiffs and defendents, depending on which hire him); a former Commanding Officer of a U.S. Special Forces company-size unit; West-Point graduate specializing in small-arms engineering; designer of a number of commercial high-end knives (and multiple patent-holder); a Company commander in Viet-Nam; and has a bunch of other nifty qualifications too... His most recent accomplishment of note is as the military and firearms technical advisor on the movie "Code Breakers" which will be premiering on ESPN on December 10. It is all about the cheating scandals at West Point in the 50's.....

BTW, I guess I should also add that he contributed many of West Point Museum's firearms, from his own private collection.

I only mention this stuff, as he never will.

If he doesn't identify himself when he joins, I'll do it by way of a welcome.

quote:

Originally posted by Alberta Canuck:
Aren't you the one who said he'd like the ammo manufacturers to include actual pressure and velocity readings on or in the box with some of their retail ammo? (So we could use it for comparative purposes in setting up/calibrating our instuments.)...

Yes indeed.

The guys using the Home Strain Gauge Systems have been using "Non-Calibrated Systems" way too long.

Right now they can take a box of factory ammo and shoot it to see what the Pressure indicates, and as long as they stay at or below that Pressure, they will have SAFE Loads.

Only problem is that they don't know what the actual Pressure of that Factory Ammo was to start with. They only know it is supposed to be slightly below SAAMI MAX, but not how much below.

And since the readings they get off the HSGSs can vary considerably due to the Set-Up, actual Calibration Ammo would be a great help for them.
---

I get the NRA American Hunter, so if it is in that magazine I'll see it. By the way, this magazine has made some HUGE improvements in content over the past couple of years. Lots of really fine articles and stories. I am really glad to see it recover from what it was just a few years ago.

Sounds like your buddy has an excellent background and look forward to him coming to AR(if we agree on things ).

Thanks AC. It should be a big help for all the HSGS users.

I will bet my last dollar that liability attorneys will never allow that information to be put on a box of ammo. Their philosophy is that “no information“ is much easier to defend in court than information that can be challenged, critiqued, or that requires technical explanation to a jury of lay people.

I have been told that Hornady will supply the lot's pressure if you call them and give the lot number. However, I haven't shot store-bought ammo in 25 years and don't plan to start now.

Several questions pop up. In the unlikely event that manufacturers did put a pressure number on the box, would it be the average pressure or the maximum pressure (and for that matter, are the pressures published in loadbooks an average or a maximum)? As those of who use those non-calibrated systems have found out, there may be considerable shot to shot variation. It seems likely that the manufacturers would have to play it safe and go by some kind of maximum instead of an average.

Another thing that those of us who use non-calibrated systems have discovered, is that pressures are influenced by the chamber dimensions. For example, I recently tried changing the freebore diameter in my '06 from 0.3100" to 0.3130" and saw a 5000 - 10,000 psi reduction in pressure with most loads. At least one other experimenter has reported similar results. Since chamber dimensions do vary considerably on mass produced rifles, using ammo that has been calibrated on a different gun to calibrate your strain gage -- or your case head expansion measurements -- could still result in 5000 - 10,000 psi error.

Hey Rick, From a Legal standpoint, it seems to me it would be in the manufacturers benefit to list the Average Pressure and Variation of a Lot on their ammo. It would give "validity" to their side that they had Tested the Pressure and know for a fact it met the SAAMI Requirements.

But, I also though a dope-smoking, adulterous, lying, draft-dodger would never be in the White House.
---

There seems to be a lot of confusion on what constitutes Calibration and it doesn't need to be that way.

Some of that confusion began when people started believing they could take a box of Factory Ammo and "Calibrate" their HSGSs with whatever value their Strain Gauges said it was. The problem with this is they do not know what the Pressure of the Factory Ammo actually is. This was another "denton doozie" and has absolutely nothing to do with "Calibration to a known Standard".

Since SAAMI Calibration Ammo is not available at a reasonable cost, most HSGS users use repetitive firing of Factory Ammo to establish a Reference Level, but it just isn't Calibration.

Normally the person that buys an HSGS really has no idea of all the problems associated with them. But that is a separate issue. Once the HSGS is bought, the chamber dimensions must be measured and the Strain Gauge glued on the receiver. Then the dimensional info is entered into the HSGS and it is ready to go.

And as a given, we all must recognize that 99.95% of the rifles produced by the factories(not SAKO's exploding rifles) are properly designed to work and function with Ammo(Factory or Reloads) meeting the SAAMI Pressure Standard for each cartridge.

So, lets say there are three guys with identical rifles chambered for the infamous 300BOGUS which has a SAAMI Max of 65Kpsi. They each have identical HSGSs and each has a box of Factory Ammo which is all from the same Lot. They all show up at the Range on the same day, set up their equipment, fall over the wires a few times, endure the laughter about the JB Weld holding the Strain Gauges on the receivers(a denton doozie) and begin firing the Factory Ammo.

It is REALLY GOOD Factory Ammo and no other HIGH Pressure Indicators are experienced or noticed. No Stiff Bolt Lift, no Flat/Cratered Primers, no Excessive Velocity, PRE is OK, etc.

Here is what each HSGS owner finds:

A. Shooter A has and Average Pressure of 60Kpsi ± 1,500PSI.
B. Shooter B has and Average Pressure of 65Kpsi ± 1,500PSI.
C. Shooter C has and Average Pressure of 70Kpsi ± 1,500PSI.

Is each of the Shooters SAFE with the Ammo?
Is that information at all useful to them?
What can they do with it?
Are they Calibrated?
(My answers are at the bottom.)

---

Now, concerning Calibration, this may help some folks understand why it can be a benefit.

All manufacturers must have Calibration Standards so what they "make", works with what other totally different companies "make". You can think of a 15" Goodyear tire fitting on anyone’s 15" wheel because the dimension measuring equipment Calibration can all be traced back to one place – the National Bureau of Standards. Same for a 30cal Hornady bullet fitting properly within the bore of a 308Win Ruger, Remington, Savage or Winchester rifle. All dimension measuring equipment traces back to the NBS.

In order for HSGSs to have credible value(different from a useful value) in relation to the Powder and Bullet Manufacturers Manuals, their Calibration must all trace back to the exact same place – SAAMI. Otherwise, you really do not know what the "actual" Pressure is.

If the same three shooters above had relatively inexpensive Calibration Ammo available they could either create a "Tare Table" to compensate for the difference, or "reset the input to the HSGSs" so they indicate what the Calibration Ammo is supposed to indicate. In this situation, they not only know when to STOP adding Powder to be in compliance with the SAAMI Specs, but they are in fact Calibrated all the way back to SAAMI.

You will still have some barrels that are what we call "Slow and Fast", but it has nothing to do with being Calibrated back to SAAMI.
---

Answers for the Factory Ammo results(non-calibration ammo).

Is each of the Shooters SAFE with the Ammo? Yes indeed, because all the Factory Ammo is from the same Lot and no other Pressure Indicators were experienced or noticed. The variation in the Average Pressure seen by each Shooter is simply due to the Set-Up data being slightly incorrect as well as the Chamber and Bore dimensions in each rifle being slightly different from rifle to rifle.

Is that information at all useful to them? Yes indeed. They know that even though the Factory Ammo is not Calibration Ammo, that the Factories manufacture it to either meet SAAMI Standards or be slightly below SAAMI Standards.

What can they do with it? As long as they keep their "Reloads" at or below the values they recorded, they know they are at or below SAAMI Standards.

They also could go back and re-set the input data to the HSGS so it better reflects the 65Kpsi. The key here is to realize they really do not know what the actual pressure of the Factory Ammo was. So, the value they re-set the HSGS to - is for Reference Only - not an accurate or quotable Pressure value.

Are they Calibrated? No. Since they don't know what the actual Pressure was in the Factory Ammo, they are not Calibrated.

Hot Core, You should be ashamed to speak of
President Bush in that manner. Now that his lies are catching up with him, he needs all the support he can get.
good luck!

Hot Core,

Talk to any liability lawyer and they will tell you that it is far safer and easier to just have a company state that “ALL†their ammunition is continually tested and checked and falls within industry safety standards for pressure, than it is to put some arbitrary average pressure figure on the boxes.

The minute some witness says “average pressure†the other side is going to run with it. Average pressure at what temperature... at what elevation...in what weapon...what was the highest and the lowest pressure making up the average? These are all questions that you do not want your clients to have to get into if you can avoid it.

Like it or not, we live in a country where anyone manufacturing anything is one accident, or one idiot, away from a law suit that can destroy their business and their lives.

The only problem I see with this is the pressure value of the ammo will only be valid in the barrel/chamber it was verified in. Change the barrel or chamber geometery and the pressure of the ammo will change. The factories can`t produce ammo and state the pressure and have it be true for every rifle it will be fired in. One doesn`t load ammo to a given pressure they load it to a given pressure in a give spec barrel/chamber at a set temp and atmospheric conditions. Loadings that rate say 60K in a test barrel could acually give 65K or 50K in another chamber. All the pressure values would be true produced pressure, but none would be the same as the other.

quote:

Originally posted by Hot Core:
,,,,is for Reference Only - not an accurate or quotable Pressure value.

Are they Calibrated? No. Since they don't know what the actual Pressure was in the Factory Ammo, they are not Calibrated.

I'll ask this one last time, assuming you might answer it..

do you calibrate your calipers EACH time you use them to measure something, from a certified reference block?

no, you don't.. but you assume it's close enough.


have a nice night

jeffe

HOTCORE-HAWKINS--Bet you left-wingers wish we were in AL GORES second term-- i am certain things would be great--but dont dispare you can vote for HILLARY

Down with George Bush. Osama bin Clinton for President. Never thought you'd see so many Liberal enlightened types supporting the freedom of expression of fascist pre-Cro-Magnon types did you. Sorry to hi-jack the thread.

Perhaps you guys missed it...but you have to scroll down a bit further for the Political forum.