Third time's a charm... Range report on John's MAI

Started by gitano, April 08, 2005, 08:32:26 PM

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gitano

Got back to the range today with, among others, John's .338 MAI. This time with a pressure gauge attached and the 'scope securely fastened. What a difference tight screws make. :)
 
Attached are the pictures - I've even condensed them more. Be sure to look at the whole picture. Below are the 'numbers'.
 
.338 MAI
200 grain Combined Technology Ballistic Silvertip
54.0 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2795 fps N=6
Standar Deviation - 13.0 fps
Average Chamber Pressure in PSIA - 56,300 PSIA
Standard Deviation - 1,105
 
.338 MAI
200 grain Combined Technology Ballistic Silvertip
54.0 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2805 fps N=3
Standard Deviation - 8.6 fps
Average Chamber Pressure in PSIA - 56,150 PSIA
Standard Deviation - 1,660
 
.338 MAI
200 grain Combined Technology Ballistic Silvertip
54.0 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2785 fps N=3
Standard Deviation - 7.5 fps
Average Chamber Pressure in PSIA - 56,460 PSIA
Standard Deviation - 469
 
.338 MAI
200 grain Combined Technology Ballistic Silvertip
54.5 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2824 fps N=6
Standard Deviation - 12.1 fps
Average Chamber Pressure in PSIA - 59,430 PSIA
Standard Deviation - 1,152
 
.338 MAI
200 grain Combined Technology Ballistic Silvertip
54.5 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2817 fps N=3
Standard Deviation - 5.0 fps
Average Chamber Pressure in PSIA - 58,610 PSIA
Standard Deviation - 1,034
 
.338 MAI
200 grain Combined Technology Ballistic Silvertip
54.5 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2830 fps N=3
Standard Deviation - 14.7 fps
Average Chamber Pressure in PSIA - 60,250 PSIA
Standard Deviation - 474
 
While I'm not too excited about the gauged pressures for the 54.5 grain charge, the cases were showing absolutely no pressure signs and there were no other signs of pressure whatsoever. As you can see from the targets, the 54.5 charge gave the best 3-shot groups. That being the case, I'll leave it to John to make his own choice regarding charges.
 
I shot the MAI, a .338 WM, two 8x57s and 56 rounds of .45-70. Then I came home and processed this data. I'm pooped. I'll post the pressure curves later.
 
Paul
Be nicer than necessary.

Hunterbug

Looks alot better with tight scope mounts. Thoes are some great groups. It looks to me like 54.0gr is a great load. Spectacular performance given the powder to bullet weight ratio and pretty good velocity.  Looks like you guys have a winner.
Ask not what your government can do for you. Ask how your government can go away and get out of your life.
 
 
The unarmed man is is not only defenseless, he is also contemptible.
Niccolo Machiavelli

gitano

You might want to check the second and third graphs again. The scale was a little off on the second (first 3-shot sub-group of 54 grains), and there was an error in bullet-hole placement on the third (second 3-shot sub-group of 54 grains). Also, I don't know why, but the image editor (on my end) is cutting the bottom off of the first graph (the whole 6-shot group). The area of the ellipse for that group is 3.736 square inches.
 
Pressure traces to come later.
 
Paul
Be nicer than necessary.

gitano

#3
Here are the pressure curves for the 54 and 54.5 loads. As you can see, the 54 grain load appears to be more stable. Hard to say for sure that this was purely a function of charge. The 54 grain cartridges were shot first, and while the bbl was by no means 'hot', it was warmer for the 54.5 grain loads than for the 54 grain ones. A dry patch was run through the bbl prior to the start of each 6-shot group.
 
Paul
Be nicer than necessary.

LLANOJOHN (deceased)

:D Gitano,

Good work there, amigo!  Pressure traces have always held a certain facination for me.  And yep...bases on the velocity/pressure data we have seen so far, the 54.0 grain load looks to be my best choice.  Will give it more thought and consideration as always.
 
Ol' John..:D :D :D
Life Member-NRA-TSRA
Riflesmith-Bolt & Lever Centerfires Only
Left-Hand Creek Rifles
Mark Twain was right-"There is no such thing as too much good whiskey!"
My best advice.."Best to stay outta trees and offa windmills!"

Jay Edward (deceased)

Great thread Paul...I love all the detailed information you put up.  Helps me get a handle on your thinking.




gitano

Let's revisit some of these numbers. Let me start by saying that sample sizes of '3' are so small as to be practically useless, but there may be a 'trend' developing with 6 or 12 samples.
 
(I noticed another typo in the initial post - the last set of 3-shot numbers for the 54.5 grain load read "54.o". I've changed it in this post, and when I'm finished here, I'll correct it in the original.)
 
Quote from: gitano54.0 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2795 fps N=6
Standar Deviation - 13.0 fps
Average Chamber Pressure in PSIA - 56,300 PSIA
Standard Deviation - 1,105
 
54.0 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2805 fps N=3
Standard Deviation - 8.6 fps
Average Chamber Pressure in PSIA - 56,150 PSIA
Standard Deviation - 1,660
 
54.0 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2785 fps N=3
Standard Deviation - 7.5 fps
Average Chamber Pressure in PSIA - 56,460 PSIA
Standard Deviation - 469
 
54.5 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2824 fps N=6
Standard Deviation - 12.1 fps
Average Chamber Pressure in PSIA - 59,430 PSIA
Standard Deviation - 1,152
 
54.5 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2817 fps N=3
Standard Deviation - 5.0 fps
Average Chamber Pressure in PSIA - 58,610 PSIA
Standard Deviation - 1,034
 
54.5 grains of Vihtavouri N-150 - CCI 250 primer
Average muzzle velocity - 2830 fps N=3
Standard Deviation - 14.7 fps
Average Chamber Pressure in PSIA - 60,250 PSIA
Standard Deviation - 474
 
Paul
First, just a brief introduction to another technical statistical term - "Coefficient of Variation", or CV. The CV is the standard deviation divided by the mean (average) then expressed (usually) as a percentage. Personally, I find the CV useless in most cases, but in some cases where 'apples and apples' are being compared, the CV might shed an extra few photons of light.
 
The CVs for peak pressures above are:
 
54.0 6-shot aggregate - (1105/56300) = 1.96%
54.0 1st 3-shot group - (1660/56150) = 2.96%
54.0 2nd 3-shot group - (499/56460) = 0.83%
 
54.5 6-shot aggregate - (1152/59430) = 1.94%
54.5 1st 3-shot group - (1034/58610) = 1.76%
54.5 2nd 3-shot group - (474/60250) = 0.79%
 
Notice the similarity in the trends of the two groups. The CVs for the aggregates are surprisingly similar - 0.0196 and 0.0194. Interesting enough on its own, but what's more interesting to me, is the trend as the bbl heats. Note that the first three shots from the bbl in the 54 grain load is twice that of the last three shots, and in the case of the 54.5 grain load it's more than three times larger. This suggests, (weakly because of sample size), that this rifle/cartridge/load combination "likes things a little warm". (Bodes well for Texas use. :) )
 
I don't want to mislead here... The peak pressure value (and it's standard deviation) are not the 'end all' WRT evaluating the variability of the pressure data. As can be seen from the graphs, rise-times in the 54.5 group are substantially more variable than for the 54.0 group. That means, that the bullet is probably moving down the barrel differently for each of those differing rise-times, and may be exiting the bbl at different points in the barrel's vibratory cycle. Teasing out the "truth" on that issue would require a FAR larger sample size. However, knowing that would likely lead to a truly 'tuned' charge and likely a very precisely shooting rifle.
 
I tend to gravitate toward this kind of analysis, because it is not confounded by the variance induced by my inability to shoot "perfectly". In other words, neither the output of the chronograph nor the pressure gauge are affected by my ability to "squeeze" the trigger, nor how well I can see, nor whether I 'doped' a changing wind correctly. Looking at group size has primarily one value for me... my performance. After I determine how the rifle performs, as independent of the shooter as I can determine, then I can evaluate my shooting performance.
 
Over the years, my performance has remained fairly consistent regardless of the rifle I was shooting... I can put shots inside a 1" circle pretty consistently if the gun can. Since I don't shoot competitively, 1 MOA has always been 'good enough' for me. As I age, it is inevitable that I will at some point no longer be a 'minute-of-an-angle' shooter. I'll just have to live with that.
 
There's one more piece of analysis to which 'yous guys' will be subjected. That's my calculation of the 'Figure of Merit' for John's .338 Mauser Ackly Improved. Coming soon.
 
Paul
Be nicer than necessary.

gitano

So here's the last of the number-crunching I'll subject you to. Unfortunately, it requires a bit of a foundation to be laid. Please bear with me - or don't. Nobody's forcing you to read this. :)

You've already seen the first piece of the final analysis... that's the calculated area of the 95% prediction ellipse in units of square inches. This value is the "accuracy" value input into a program I call the Figure of Merit. Strictly for my own use, I wrote a program that would help me decide objectively, as opposed to emotionally, between two or more bullets in the same cartridge from the same gun, or if I just felt argumentative, (my gun/cartridge is better than yours), between two or more rifles.
 
The coefficients (weighting factors) for the input parameters were subjectively chosen by me based on what I think is important when evaluating a rifle/cartridge/bullet combination. The relative importance was decided subjectively, but the analysis is purely objective.
 
For me, ALL elements under consideration, up to a point, are subordinate to precision (Also Known As accuracy). Kinetic energy comes second... a distant second, but second none-the-less. Next is how "flat" the cartridge/bullet combination shoots. Next is recoil. Since "percieved" recoil is unmeasurable, this recoil is the calculated recoil. Next is the maximum Point Blank Range. This is the range at which the bullet has dropped to 3 inches below the line of sight, while having been sighted in so that the maximum height above the line of sight was also 3 inches, yielding a six-inch vertical target size. The last parameter is a "lethality" factor. In order to reduce the arguing over whether "my" lethality factor was "right", I simply took one from Peterson's Hunting, January 1996, page 53.
 
Not all of the models for the parameters are linear. (Meaning, for example, that a decrease in "flatness" from 1.5 inches to 1 inch does not result in the same change on the coefficient as does a change from 3.5 inches to 3.) The height coefficient is actually multiplied by the inverse of the log of the standard deviation of the height over the whole range (muzzle to max range). Since the significance of recoil from 0 to about 7 or 8 foot-pound is very small relative to the difference between 20 and 28 foot-pounds, the recoil model is also non-linear.
 
Finally, as the psycho-babblers say, "everything is relative", so I had to choose some "standard". Again, wishing not to argue over trivialities, I chose an 8.5 pound .30-06 shooting a 180 grain bullet ahead of a 55.5 grain charge, at 2700 feet per second at the muzzle. This is an arbitrarily chosen STANDARD, NOT what somebody can MAKE an '06 and a 180 grain bullet do. It's just a ruler most of us recognize. The standard group is a 3-shot group where the max spread is exactly one inch between each bullethole. (A graph is provided below.) The elevation chosen was 1000 feet above sea level, and the ambient temperature was 50 degrees Fahrenheit.
 
Below are the charts from the "Standard 3-shot Group", and the "Standard Figure of Merit" for the above described '06. As you can see, the value is 1000. Not an accident. I set it up that way. Therefore, after I "run" a different rifle/cartridge/bullet combination through the program, it's FoM tells you how it compares to the "standard" '06.
 
First I'll present the "standards", then the results for John's .338 MAI.
 
Paul
Be nicer than necessary.

gitano

#8
OK, on to the 'final chapter'... John's .338 MAI. Loaded, John's gun weighs 9.625 pounds. The bullet is a 200 grain Combined Technology Ballistic Silvertip with a ballistic coefficient of .400. The first charge for consideration is the 54.0 grains of Vihtavouri N-150. While the elevation at the range isn't 1000 ft above sea level, we'll use that value because we want to compare apples to apples. The "accuracy" value we will use is from the 6-shot group as it is a better "known" than either of the 3-shot groups are.
 
The 'accuracy' value for the 54.0 grain charge is 3.736 square inches. After all things considered, the FoM is 1606.
 
The 'accuracy' value for the 54.5 grain charge is 5.625 square inches. So, even considering that the velocity is 29 feet per second faster, and all other things are equal, the FoM is only 1561. Gives you some idea of how important I consider 'accuracy'.
 
Anyway, have a look at the attached graphs and numbers and feel free to ask questions or make comments.
 
This is the last of the 'heavy' numbers.
 
Paul
 
OOPS, got in a hurry and put in the wrong gun weight. It's correct now and the FoMs moved accordingly.
Be nicer than necessary.

Hunterbug

I'm so glad that gitano is around to crunch these numbers for us because if it was up to me to do it we would be in a world of trouble. ;) 54.0 seems to be the ticket. The minimal gain in velocity by going up that extra .5gr is far outweighed by the higher pressure and accuracy factors. The speed and power that is being achieved for the amount of powder being used is impressive. The 54.0gr load is only a hair over 100fps behind my 338 Win Mag with about 10gr of powder less with the same bullet weight. The more that I see this the more intrigued I become.
Ask not what your government can do for you. Ask how your government can go away and get out of your life.
 
 
The unarmed man is is not only defenseless, he is also contemptible.
Niccolo Machiavelli

gitano

Thanks HB. I like doing it.
 
This is the kind of 'thing' I'm talking about when I talk about "efficiency". A similar bullet performing similarly with less powder and less other 'stuff' (like recoil for example) too. Makes me start thinking about hanging up the .338 Win Mag. Of course to some, speed is everything. That's OK by me... just not for me.
 
As I was doing this last workup, I got to thinking that maybe I should include the variability in the average velocity, and parameters about pressure and its variability. All too often though, real pressure data won't be available.
 
Anyway, that's it for now on John's .338 MAI. I'm gonna make up a 'book' of this analysis (plus a bit more :) ) for John, and send him the whole package. This is quite a cartridge, and as far as I can tell, no one's thunk this one up before. Kind of amazing in itself.
 
Paul
Be nicer than necessary.

LLANOJOHN (deceased)

#11
Well, at age 62+, I am still a-larnin'! Just installed my new scanner, copier, printer and fax machine. Lets see if I can transfer some data and reamer info.
 
HEY! HEY! HEY!   I done dood it!  Now if "ol' dummy" can remember how "HE DONE DOOD IT!"   VE GIT SO SOON OLD'T AND SO LATE SCHMART!

Ol' John..(duhhhh!)..:confused: ;) :D
Life Member-NRA-TSRA
Riflesmith-Bolt & Lever Centerfires Only
Left-Hand Creek Rifles
Mark Twain was right-"There is no such thing as too much good whiskey!"
My best advice.."Best to stay outta trees and offa windmills!"

drinksgin (deceased)

#12
John;
Either you did something else or I did, it will only go to a temp file.
Don
 
Don, bear with me buddy!  I don't even know what a "temp" file is!!!!  One of these days I just might become "edjamacated"....at least there is hope!

Ol' John....;)
NRA life, TSRA life, SAF life, GOA, CCRKBA, DEF -CON

LLANOJOHN (deceased)

Paul sent me a pic of the cartridge and bullets with a 338 WM for comparison.
Life Member-NRA-TSRA
Riflesmith-Bolt & Lever Centerfires Only
Left-Hand Creek Rifles
Mark Twain was right-"There is no such thing as too much good whiskey!"
My best advice.."Best to stay outta trees and offa windmills!"

Brithunter

Hi All,

       Gentlemen, may I congratulate you. I am deeply impressed :cool:  this is one heck of a performance package.
Go Get them Floyd!

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