From the NRA pub _Handloading_, "Some Simplified Interior Ballistics for Handloaders" by William C. Davis:

A useful approximation: "Chamber pressure is proportional to the square of the loading density."

Now for the Varget Load pressures:

Mr. Davis's method is based on the Powley equation and uses a table of expansion ratio versus "mass ratio" (powder charge weight to bullet weight in grains) as a simplifying reference for calculating K1, K2, and K3 for plugging into: P = K1 x K2/K3

This gives pressures in PSI, and they compare favorably to Dupont measurements of pressure in PSI by a crusher-type guage.

Pressures calculated by this method for cartridges of caliber .25 to .338 were within 10% of measured pressures, about equally divided, high and low.

For smaller calibers, the calculated pressures were typically lower than the measured pressures, about 4% lower for 6mm/.243 calibers, and about 8% for .22 calibers.

For calibers greater than .338, calculated pressures were typically higher than measured pressures, about 7% for .35 caliber and about 15% higher for the .458 winchester Magnum.

The .375 H&H was an exception to the trend, and gave calculated pressures in very good agreement with the measured pressures.

I'll bet the .404 Jeffery is much like the .375 H&H in this regard: Actual pressures are in very good agreement with those calculated by this method.

Or maybe the actual pressures for the .404 Jeffery are even lower than these calculated using the Davis method???:

**************************************
Woodleigh 400 grain RNSP/81.0 grains Varget/2400 fps ... 49,400 psi

North Fork 380 grain SP/83.0 grains Varget/2525 fps ... 52,000 psi

North Fork 340 grain SP/87.6 grains Varget/2700 fps ... 61,300 psi
*******************************

CIP pressure standards for the .404 Jeffery:
Max average = 52,975 psi
Max individual = 60,929 psi

Just some food for thought on .404 Jeffery pressures.

After seeing the sectioned Norma .404 Jeffery brass compared to the .416 Remington brass (thanks to Alf) there is no doubt that in modern rifles, the .404 Jeffery can do a lot more than the standards for antique rifles established by CIP.

Well, don't leave us hanging, what were the values and how did you calculate K1...K3?

I feel even with good Norma Brass I will not push the barrow with my 1909 m98 .404 (when it arrives) I will settle for 2300 fps with the 400 gr woodleigh. I reckon 80 gr of AR2208 will get me there..........................AR2208 is Varget for all intensive purposes I think.

Will,
If you insist, then bear with me through the definitions of terms and example calculation:

I = 81.0 grains ... (charge of Varget Extreme)
W = 85.0 grains ... (100% load density charge with 400 grain Woodleigh RNSP and Varget Extreme)
G = 400 grains ... bullet weight

R = expansion ratio = (Q + U)/U

Q = volume of bore, effective bore volume in cubic inches
U = volume of powder charge in cubic inches
W = water capacity of powder chamber, grains of water
T = bullet travel in inches
E = barrel length inches
S = seating depth, inches = 0.640" with this load
C = case length (trim to 2.865")

T = E + S - C

Q = 0.773 x T x D^2

D = bullet diameter = groove diameter of barrel, inches

A = mass ratio = charge weight/bullet weight = 81/400 = 0.2025

V = 2400 fps muzzle velocity

K1 = .0142 x I x F2 x V^2
K2 = .53 x (G/I) + .26
K3 = W x (R-1.0)

F2 is read off a table in the text of the quoted article: get the book and follow along with me now:

To get W, we need to calculate the volume of the bullet seated into the case: the volume of a cylinder 0.640" height and 0.423" diameter = 0.1405 cubic inch

Water weight of .1405 cubic inch = 15.4 grains.

W = case volume in water below seated bullets = 115 - 15.4 = 99.6 grains of water.

E = barrel length = 24"

Back to T:
T = 24" + 0.640" - 2.865" = 21.775"

Q = 0.773 x 21.775" x 0.1789 = 3.01 cubic inches, for a 24" barreled .404 Jeffery.

Back to K1:
K1 = 0.142 x 81.0 x F2
F2 = 1.97 from Table 4 (plot of expansion ratio verus mass ratio)

K1 = 13,051,549

K2 = .53 x (400/81) + .26 = 2.88

K3 = W x (R - 1.0) = 99.6 x (8.64 -1.0) = 761

where R = Expansion ratio = (Q + U))/U

U = volume of cartridge powder chamber in cubic inches = volume of 99.6 grains of water

99.6 grains x 1 gram/15.4 grains = 6.47 grams water = 6.47 cc water x (1 cubic inch)/(16.4 cc) = 0.394 cubic inch

R = (3.01 + 0.394)/0.394 = 8.64 We used this above to get F2 then calculated K1.

Finally, it all comes together to give the pressure in psi:

P = K1 x (K2/K3)
P = 13,051,549 x 2.88/761 = 49,393.5 psi

For two significant figures this is 49K psi.

quote:

Originally posted by PC:
I feel even with good Norma Brass I will not push the barrow with my 1909 m98 .404 (when it arrives) I will settle for 2300 fps with the 400 gr woodleigh. I reckon 80 gr of AR2208 will get me there..........................AR2208 is Varget for all intensive purposes I think.

PC, with a 24" barrel, 78 grains of AR2208 will get you where you want to be with the 400 grain Woodleigh Weldcore RNSP. Use 77 grains of AR2208 with the 400 grain Woodleigh solid, for about 2300 fps.

Thanks RIP,

my barrel is 23 1/2" long so the 77 gr of 2208 will be the one I go for I think, I have a few cz's that can be used for hot rodding

.

Alf,
The Powley equation is the basis for the slide rule. The table used in the text is a similar "slide rule" type device (I started college using slide rules and graduated using Texas Instruments calculators in the 1970's).

This method seems to give better results than the defaulting computer programs we have seen applied to the .404 Jeffery here.

You have no arguments from me.

I agree with the low pressures in antique guns.

I am just saying there is no reason to fear a 2400 fps 400 grainer in a modern .404 Jeffery, with Norma brass.

Nor is there reason to fear a 2525 fps 380 grain North Fork in the same modern equipment.

I will stop short of recommending a 340 grain North Fork to everyone at 2700 fps, but in my rifle it is an extremely pleasant load.

quote:

Originally posted by PC:
Thanks RIP,

my barrel is 23 1/2" long so the 77 gr of 2208 will be the one I go for I think, I have a few cz's that can be used for hot rodding

If you really want to play the gentleman hunter, use 72 grains of AR2208 with a Dacron filler of 3 grains of stuffing. That might move the 400 grainers along at about 2150 fps, and be close to the original ballistics.

This latter I have not tried, but I don't think you could go wrong using that for an effective "old man's load" for a .404 Jeffery.

Alf,
As evidence that this Powley/Davis method of calculating pressures is pretty good, consider the A-Square manual pressure for the .404 Jeffery in Piezo PSI:

400 grain Dead Tough soft
80.0 grains of RL-15
2379 fps in 26" barrel
49,800 PSI

my calculation:
400 grain Woodleigh Weldcore soft
81.0 grains of Varget
2400 fps in 24" barrel
49,400 PSI

Yep, I think this method is pretty close to reality for the .404 Jeffery.

80 grains of RL-15 is mighty close to the same thing as 81 grains of Varget.

Varget Extreme is a better powder than RL-15 in my .404 Jeffery rifle, for sure.

Most burn rate tables show Varget as just a tad slower burn rate than RL-15.

.

Alf,
Sure, the old Powley equations and those before Homer are good ones. These PC internal ballistics programs are just extensions of the old methods, to be user friendly, nothing more. But the new PC programs are "dumb" in regard to defaulting when it comes to some situations beyond their set parameters.

I love the basic physics of this, and will continue to make it a hobby. Please pass along any references if you come across anything I might find access to.

Two of my loads are within CIP average chamber pressure limits by this Powley/Davis calculation:

1. 400 grain Woodleigh soft at 2400 fps using 81 grains of Varget Extreme.

2. 380 grain North Fork soft at 2525 fps using 83 grains of Varget Extreme.

As for the third load, the African Sheep Load, I can only say: Kids, don't try that at home.

I will use caution in watching my brass for that load, but I truly feel that it is safe in my rifle.

So, if I can ever get hold of a 320 grain HV from GSC, I might have a higher BC and lower PSI with a flatter shooting load yet.

Otherwise I have no facts to relate to your list of questions, but they are rhetorical, are they not?

RIP-ALF--I use a version of Homer's formula
for velocity also, that is adapted to 45 cal
and over-His original setup had big bores
with more pressure than actual.I have an expansion ratio chart all figured which saves 80% of the figuring, with a factor from the chart, to put in equation..I have factors for the pressures I expect to load up to.
IE, it is like the pressure formula in reverse.
And now I can get an extra checking procedure on my MBP chart.

CIP & SAAMI only set limits to protect their
butts for the use of their products in older
guns.. But as the man says; he can run modern pressures in his modern gun, with thick web modern brass.And modern limits are based on weakest link, the brass.And in all brass cased rounds cannon or rifle that has mainly been
the limiting factor.Ed.

Ed,
I have greater respect now for these methods of pressure calculation. I trust the longhand-refer-to-a-table-simplified-Powley-Davis method more than any of the defaulting PC software.

Your enlarged graph of MEP as a function of ME and caliber should be a great tool.

The Powley-Davis method can be used to back into some understanding of many basic relationships of pressure factors.

Yes that is the nice thing about Homer's
stuff is it gives an understanding of
internal ballistics, and factors involved, that helps you go where the computer program chickens out.Ed.

The way I redefined "W" in my example calculations was not too cool.

Here is a representation of the original William C. Davis Powley based method:

http://www.aeroballisticsonline.com/ballistics/imrpowder.html

I posted my .404 load data and results with VARGET in the Africa section.
C

RIP & Ors,

I have started & stopped my load development with 80.0gr of AR2209 or H4350 & the Woodleigh 400gr SP, Norma Cases & CCI250 for MV of 2185 fps. Pretty close to the Kynoch loads. Gives sub MOA 100yard 3 shot groups. Barrel is 24 inch Sprinter.

Just wondering with the large case capacity why Varget & not a slower powder such as H4350 (or even slower & bulkier)to get more load density? The load development talk on the Jeff seems always centered on Varget, just wondering why?

I am wary of pushing it faster cause my rifle is a custom off a Argentine 1909, the load is accurate & it regulates to the open sights.

Regards
JohnT

JohnT,
If you gotta ask, you don't wanna know.
Some of us prefer the .404 Jeffery around 2400 fps and around 50Kpsi with 400 grainers. We get that with about 95% density loads with Varget in 24" barrels: 81 grains Varget with 400 grain Woodleigh RNSP/Weldcore.

H4350 is a little bulkier than Varget, and would require 87 grains for a 100% density load to get to 2329 fps in my "loose" 24" barrel. This would be my choice for duplicating the now defunct RWS "hot load" of 400 grainer for .404 Jeffery, in my rifle. 100% density is sweet.

Your barrel may be tighter.
You may get better results with H4350 than I got.

I could get 2400 fps with H4350 using 90 grains and mild compression (104%), in my rifle.

Varget 85 grains is a 100% load with the Woodleigh.

Yep, those would be the top two powders in my rifle: H4350 Extreme is second place to Varget Extreme.

Then if you want to go to lighter bullets, 340 grainers at 2700 fps, Varget is the only way to go. Not for the timid.

BTW, I got better accuracy with Varget than with H4350. Looks like your rifle shoots almost as well as mine.

Another thing to consider is the lesser recoil with Varget/2208 versus H4350/2209.

I do with 81 grains of 2208 what I do with 90 grains of 2209.

Varget will be kinder to wood stocked rifles, especially octagenarian wood.

If I were loading for an antique .404 Jeffery, I would think about 72 grains of Varget with Dacron filler of 3-4 grains of fluff, and more gently accomplish what you do with 80 grains of the slower powder.

Your peak chamber pressures might be lower though.

John T,
Your right on...I have used IMR-4831 from 90 to a max of 95 grs. in my 404s...I still use that load after trying all the rest...I get more velocity, less pressure and a full case of powder...

Some tell me they cannot get 95 grs. in a case, in which case I think they must have very tight chambers as that load comes up half way in the long neck of a 404 in my guns......95 grs. in my old 27" barrel got me 2653 FPS....

My hunting load has been 93grs. of IMR-4831 with any 400 gr. bullet for the last 30 years, as I recall...I have pretty much settled on that, mostly because of the recoil factor, and its a mild low pressure load...

I have shot more than several Cape buffalo with the 95 gr. load from time to time, and also with the 93 gr. load and no apparant difference could I tell, so I go with the lessor load.....I do the same with my .470 N.E.....

Of course, Ray uses a 3 foot long drop tube, has a 28" barrel, and a chronograph with built in velocity adjustment factor that varies with the phase of the moon and planetary alignment. His .404 Jeffery really sings during a total eclipse of the sun when fired over the chronograph on the Zambia side of Victoria Falls.

LMAO

the 404 does nothing the 416 taylor wont...

and the taylor is a FAR cry easier to gunsmith/get parts for...

"wildcat cry"... yeah yeah, and the 404 was one, too

jeffe