16ga.com ~ View topic - M-A-P

here's a question for Mark and the other techs here . We often mention MAP (max avg pressure) , and my question is : what is the standard for what is to be the MAX in the deviation . In other words is 50 psi over ok , 100 psi over ok - what is considered to be the max max !? I know one of Mikey C's loads is mentioned again , it avged 100psi over MAP . He liked it and most others would hesitate to consider it . Was just wondering if there is a top limit .

Joined: 04 Mar 2019 Posts: 1844 Location: Central ND

SAAMI Standards are written for new ammunition only. There are three levels afforded the ammunition manufacturers, Maximum Average Pressure, Maximum Probable Lot Mean and Maximum Probable Sample Mean. In case of a deviation from MAP, MPLM and MPSM are used to qualify a lot of ammunition. There are no such provisions for reloads. It is widely understood that MAP is the only average pressure level suggested for reloads. Of course that only applies if someone wants to follow the industry.

SAAMI Maximum Average Pressure for each gauge IS the maximum that you should follow when reloading. In the 16 gauge that means an average pressure of 11,500 PSI.

As far as deviation goes, for the 16 gauge as applied to new ammunition the Standard Deviation is calculated at +/- 862.5 PSI. Which means that in a 10 round test sample you can expect the individual loads to vary 862.5 PSI from the average of the entire test sample. That does not mean it SHOULD vary that much, but it could vary that much. That is a LOT of leeway, especially for light hunting or target loads.

When I was working with Tom Armbrust we held it a bit tighter and used an EV of 1,500 PSI for a 10 round test string. I still hold any load I develop to that standard.

For my own ammunition I do not exceed the SAAMI MAP or the EV of 1,500 PSI. However I will not shy away from a 16 gauge load that exhibits an average pressure of 11,500 PSI.

I do practice what I preach.

gotcha Mark ... was just wondering if in fact there was an extreme limit to which was generally used .

More on the Sporting Arms and Manufacturers Institute (SAAMI) standards
https://saami.org/technical-information/ansi-saami-standards/

1) Pellet size variations allow for +/- one pellet size (+/- .010" dia.) of variation in game loads.
A No. 6 (.110") game load could contain pellets ranging in size from No. 5 (.120") down to No. 7 (.100").
On target loads it allows for +/- ½ pellet size (+/- .005" dia.) of variation; a No. 8 (.090") target load could contain pellets ranging in size from No. 7 1/2 (.095") down to No. 8 1/2 (.085").

2) Load weight variations can range from +4% to -7% in game loads and +3% to -5% in target loads; about +/- 1/8 oz. of variation allowed per shell.

3) Pellet counts per ounce can vary by +/- 10% for both game and target loads.

4) Load velocity can vary by +/- 90 fps for both game and target loads.

5) Load pressure
Maximum average pressure for 12g and 16g 2 3/4" and 3” shotgun shells will be 11,500 PSI +/- 900 psi, with some maximum extreme variability not to exceed an uber-max of 12,500 psi +/-900 psi

6) Proof loads:
If a manufacturer uses a SAAMI proof loads, then the gun will be proofed by a lot of no less than 10 shots of ammo loaded to a maximum proof pressure of 20,500 psi +/- 900 – 4600 psi, or uber max of 25,100 PSI; and, will be similarly a MINIMUM average proof pressure of 19,000 PSI +/- 900 – 4600 psi for an absolute minimum proof of 14,400 PSI.

The Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives (CIP) standards

12g 50mm, 65mm, and 70mm “Standard Proof” lead or steel (limited to no larger than 3.25 mm and max. fps 1,300).
Numbers are transducer BAR converted to PSI.
Maximum Average Pressure 740 BAR = 10,733 psi;
Maximum Statistical Individual Pressure 850 BAR = 12,328 psi
Mean PROOF Pressure 960 BAR = 13,924 psi

Both 65 and 70 mm 16g standard is SERVICE 780 BAR or 11,313 psi;
MSIP 900 BAR or 13,053 psi;
PROOF 1020 BAR or 14,794 psi.

I couldn't find the allowed pressure variability in the CIP standards

The critical question however is "For what load was my gun designed?" and we have good data now even for turn-of-the-century doubles in that regard.

Joined: 04 Mar 2019 Posts: 1844 Location: Central ND

revdocdrew,

Be careful to understand this statement correctly:

"4) Load velocity can vary by +/- 90 fps for both game and target loads."

Not exactly as it appears on face value.

What that statement means is that the loads in a box of shells can average +/- 90 FPS of the velocity printed on that box of ammo. NOT that the loads in the box can vary +/- 90 FPS from each other giving a possible EV of 180 FPS, which some folks steadfastly believe it means.

The +/- 90 FPS statement is how the ammunition factories got around the ATA's rule of using ammunition with a maximum of a 1 1/8 oz. 3 dram 12 gauge load and got the velocity of their "Handicap" loads from 1,250 FPS to 1,290 FPS and stayed within the rules.

A standard 12 gauge, 3 dram 1 1/8 oz. load has a velocity of 1,200 FPS.

Here is the entire statement concerning velocity:

VELOCITY AND PRESSURE:
VELOCITY DATA INTERPRETATION

Velocity recommendations are stated on the basis of a nominal lot mean velocity as measured using equipment in accordance with the requirements of Section III and the procedures detailed in Section II. Due to the fact that sporting firearms for general distribution are typically manufactured to dimensional tolerances greater than those specified for test barrels, there should be no expectation that these velocities can be duplicated from any test utilizing firearms. This situation is further
confounded by discrepancies in barrel length. Furthermore, once ammunition has left the control of the manufacturer, storage conditions outside those recommended by the manufacturer may cause variations in the velocity as measured using test equipment and procedures which conform to the requirements of this Manual.

The values presented on pages 6ff are recommended values for the use of ammunition producers at the time of manufacture. It is the responsibility of the manufacturer to establish sample sizes, sampling frequencies, and tolerances to ensure the performance of the ammunition obtained by the ultimate user meets all applicable safety and functional standards. Of particular importance in establishing velocity tolerances is the understanding that velocities significantly higher than the nominal lot mean can cause actual maximum range performance to exceed expected values.

Ammunition tested subsequent to manufacture using equipment and procedures conforming to these guidelines can be expected to produce velocities within a tolerance of ±90 fps of the tabulated values.

Joined: 04 Mar 2019 Posts: 1844 Location: Central ND

revdocdrew,

The statement below is misleading:

"6) Proof loads:
If a manufacturer uses a SAAMI proof loads, then the gun will be proofed by a lot of no less than 10 shots of ammo loaded to a maximum proof pressure of 20,500 psi +/- 900 – 4600 psi, or uber max of 25,100 PSI; and, will be similarly a MINIMUM average proof pressure of 19,000 PSI +/- 900 – 4600 psi for an absolute minimum proof of 14,400 PSI."

This statement mixes proof load pressures with Maximum Extreme Variation. Maximum Extreme Variation is truly extreme. While the statements about MEV are written into the Standard, I have never seen an EV, of 4,600 PSI even with steel or other pellet types and maximum pellet and powder payloads. 2,500 PSI is the maximum I have ever seen and those loads exhibiting that type of variation were never published.

No manufacturer that I am aware of fires 10 proof loads in their new shotguns for proof testing. To the best of my knowledge it is one proof load per firearm, with a few standard rounds to check that the action is operating correctly. I know this from being around Winchester and Mossberg in New Haven CT. Now maybe things have changed and if they have I apologize for misleading anyone. I believe we are confusing a 10 round test sample, for testing the pressure of a given lot of proof ammunition with how many proof loads a new shotgun sees.

For proper interpretation we have to understand the SAAMI Standards, the intent of the standards AND how these standards are applied to the manufacture of NEW ammunition. Just reading the Standards and taking them at face value is very misleading.

On top of that, with the exception of the individual MAP values for each gauge/bore and the test equipment used to check pressure and velocity, very little of the SAAMI Standards apply to reloading nor were they meant to be.

I am not trying to be argumentative, I am just trying to keep what we as reloaders can do and what the ammo manufacturers do separate.

It is also important to recognize that SAAMI is a voluntary trade organization; as are the "standards".
CIP however carries the force of law for member nations.

BTW: The Birmingham Proof House uses ONE proof load

2006 British Rules of Proof
https://www.gunproof.com/downloads/rules-proofing
Part IV, “The Proof Load”, Number 27, Part A
Calls for a load of 30% over mean service pressure at a point 17mm or 25mm (about 1”), and at a point 162mm (6.38”) from the breech face a load of 30% over mean service pressure (at that point as determined by the Proof House).
The powder used in proof loads is not specified.
AFAIK and there was quite a discussion on DoubleGun in this regard, the pressure-distance curve of a single load is adequate; not 2 different loads/shots.

Joined: 04 Mar 2019 Posts: 1844 Location: Central ND

I've had this conversation about 'voluntary' SAAMI Standards with Randy Wakeman who seems to feel that the Standards are voluntary as in you don't have to follow them.

My question to him went something like......How voluntary are the standards if you make ammunition for the US market? They aren't voluntary as in you can choose to follow them or not. If you make ammo for the US market, you have to follow the standards, because when someone makes a mistake and does something foolish and blows up a gun, without being able to show you are following SAAMI Standards (which are certified by ANSI which is another layer altogether) your company is going to take a big hit. SAAMI didn't go out and get certified by ANSI for no reason and certainly not because their standards are only 'voluntary' to follow.

The term voluntary means that IF you own a company that makes ammunition there is no law saying you have to follow the SAAMI Standards. That doesn't mean that it is smart to not follow the standards. There is no other set of standards to follow and to not have any standards to follow leaves your butt hanging out in midair just asking to have it kicked.

As I stated before, we have to understand the SAAMI Standards, understand the intent of the standards and then understand how to apply those standards to the manufacture of ammunition in the US market. Only a small portion of the standards apply to reloading, which is what this thread was actually about.

Joined: 16 Jul 2015 Posts: 2126 Location: Hudson,Wy

Mark, you had a discussion with Wakeman? About anything scientific? I am so, so sorry for you. I can just see that guy up late at night with his master load blueprints...waiting for supplies to arrive from ACME while the Road Runner sleeps peacefully unconcerned.

Joined: 04 Mar 2019 Posts: 1844 Location: Central ND

LMAO!!!

The fact that a personal injury lawyer will ask an ammo maker why they didn't follow the "voluntary" standard makes them less than "voluntary".
Likewise, a personal injury lawyer will ask a reloader in the event of a burst if they followed a published recipe, and very likely why they elected not to send their reloads for ballistic testing in light of the documented variation from the published recipes.

Anyway - numbers are of interest to a few of us Wink

but IMHO if 100 or 200 psi increase matters, I'd find a different recipe. Even turn-of-the-century shotguns were proved at least 40% higher than the pressure of the period recommended loads, so there should be a significant safety factor.

Joined: 04 Mar 2019 Posts: 1844 Location: Central ND

If you go way back into SAAMI it was an agreement between the manufacturers to set the standards. That's where the word 'Voluntary' was introduced. It was a voluntary agreement between the manufacturers not voluntary that they followed the Standards. I can't even think about how messed up it would be if there were standards that you could use if you felt like it.

To this day the manufacturers are still SAAMI, it is not a separate group that makes and updates the Standards. ANSI gives the Standards credibility.

CIP........ever see a government run an entity very well? Me either.

thanx guys for the back and forth . there is never a simple answer to anything it seems , but good to have an idea of what things should be or the true guidelines ! .... mark ,is it still real dry out there ?

Joined: 04 Mar 2019 Posts: 1844 Location: Central ND

April we had a blizzard. May June and the first of July, we had some rain. Since mid-July it has been dry. Haven't mowed the lawn in at least 3 weeks(at least I saved a little diesel lol).......nothing in the forecast that points to any amount of rain in the next two weeks. From what I understand, this is a fairly normal year.

I sure hope it starts to cool down a bit. Been in the 80's and 90's and that is too hot to run the dogs any significant amount.

Dove season opens in 2 weeks and then grouse and huns a week later. Probably use the first few weeks of grouse season to get the dogs up to speed. A little each day even if I don't actually hunt.