When Did 357 SAAMI Pressure Change?


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Jaywalker
December 24, 2012, 12:23 PM
I understand the SAAMI pressure for the 357 changed in the 1980s or 1990s, down to its present 35,000. Does anyone know what year?

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murf
December 24, 2012, 12:28 PM
1992, or 1993.

murf

Guillermo
December 24, 2012, 12:50 PM
Was it 37000 before?

ArchAngelCD
December 24, 2012, 12:54 PM
Was it 37000 before?
I think it was 40,000 PSI.

I think SAAMI changed the pressures when the ultra light .357 Magnum carry guns became popular. (think 12oz S&W M340)

Guillermo
December 24, 2012, 12:56 PM
Thank you ArchAngel

Jaywalker
December 24, 2012, 02:43 PM
Thanks. I'd read that S&W wanted it reduced due to the problems with the 125 gr in the K-frames, M-19 and M-66, but I suspect its use in the J-frames had a influence. It could also have been the presence of better pressure transducer equipment that showed peaks instead of averages showed much higher pressure than they'd thought for years.

I'd also heard it was 47,000 somethings (psi, lup, cup, etc.) before dropping to 35K, but that doesn't mean what I read was right.

I'd shot both the 19 and the 66 with those older, higher pressure 125 gr loads. They were accurate enough, but I couldn't see using it for SD - too much flash, blast, and recoil for follow-up. Since I'd moved to semi-autos I had not heard about the reduced pressure until recently. Today's pressures might change me back.

CraigC
December 24, 2012, 03:07 PM
My info says 46,000CUP (43,500psi) to 35,000psi in 1995. Which was approximately a 25% reduction.

2zulu1
December 24, 2012, 05:26 PM
If you handload, VihtaVuori (2006) loads to the European standard of 43,500psi, same for the 41mag. :)

skidder
December 24, 2012, 05:42 PM
Thanks for the info guys.
My reloading manuals also verify there was a change. According to the copyright dates it looks to be somewhere in the 90's.

BaltimoreBoy
December 24, 2012, 06:23 PM
So, Jaywalker, you are implying that because S&W was manufacturing revolvers that didn't stand up well to the existing standard, they had SAAMI change the standard rather than fix the problem?

I knew about the 70's reduction in 38Special. Somehow this reduction in 357 had escaped me.

rcmodel
December 24, 2012, 07:30 PM
I doubt it had anything to do with S&W K-Frames.

.44 Magnum & .357 Magnum were both reduced at the same time.

I suspect it had more to do with more accurate pressure measurement methods when electronic transducers took over from copper cylinders getting hammered shorter.
And they found out what the pressure really was.

rc

Jaywalker
December 24, 2012, 07:45 PM
BaltimoreBoy,

I don't know - we see all sorts of conspiracy issues on the internet, and one I read suggested Smith might have lobbied for a change based on the K-frame very real problems with the 125 gr. 357 load. It's possible, but I think it's more likely the change in the testing methodologies cup/lup to psi using strain gauges and piezo-electric methods led to a more accurate representation of pressure. I'm certain, however, there would be no changes to any of the testing methodologies or resulting pressure standards by SAAMI without agreement by large industry manufacturers, including Smith.

Steve C
December 25, 2012, 03:23 PM
The SAAMI pressures measurements changed units from CUP (Copper Units of Pressure) to PSI (lbs per sq in). CUP's where determined using the old copper crush method that is less precise form of measurement of peak pressure and has no direct correlation to PSI. PSI measurements are determined by electronic Piezo transducers which is much more precise in determining peak pressure.

Comparing old SAAMI CUP pressures to current PSI is similar but not precisely like comparing English to Metric measurements and trying to determine if the numbers indicate a real change.

Guillermo
December 25, 2012, 04:03 PM
Steve C

The change in measuring scale came in the late 60's...not 1995.

That was a political change. Not scientific.

ArchAngelCD
December 26, 2012, 04:12 AM
If you handload, VihtaVuori (2006) loads to the European standard of 43,500psi, same for the 41mag. :)
CIP pressure limits have nothing to do with SAAMI pressure limits. CIP limits are generally higher than SAAMI limits. (in some cases what SAAMI used to be)
http://www.cip-bobp.org/

gamestalker
December 26, 2012, 03:33 PM
I read an article written by S&W some years ago about testing that they did with the 125 gr bullets being blamed for fractured forcing cones on K frames. Apparently they ran 10's of thousands of .357 H110 loads with 125 gr. jacketed bullets and had no cone failures. However, when they tried the same thing with non jacketed bullets, forcing cone failure appeared and fairly quickly, which was apparently caused by lead deposits in the cones causing pressure on the cone to fracture them.

As for the .357 mag changing max SAAMI pressures, I read that this change was primarily the result of better testing tools such as the electronic transducer, thus eliminating the CUP method and going with the highly accurate transducer pressures to PSI.

Currently I load with H110 / 296 and have and still do load and shoot gobbs of them 125 gr. jacketed bullets through my K frames with no indications that they are damaging the cones, or anything else, other than my wrists. One of my K's, a 66-2, has had thousands put through it.

GS

GS

nofishbob
December 26, 2012, 04:01 PM
There seems to be two different issues being discussed:

The method of measuring pressure, and reducing damage to guns.

I contend that if new measuring equipment came along, and more accurate pressure/time information was available, there would be no reason to reduce the loads in the absence of a desire to correct an overpressure situation that had been exposed by gun failures.

If guns were not failing at a certain load, many of which were used for decades, why reduce them when new pressure info is available?

After all, measuring chamber pressure is intended to predict a safe load for a particular cartridge.

No matter what a pressure measurement says, if the guns are failing, the pressure is too high. Conversely, if the guns are reliable at a certain load ( for thousands of rounds), it is a safe load no matter what the pressure readings are.

I am always struck by the assertion that when psi transducers became available, all .357 loads had to be reduced because all these years we were overloading our revolvers but somehow we were just lucky that the guns did not blow up on us.

Bob

showmebob
December 26, 2012, 04:01 PM
Ok, I'm not following this.
Since the transducer is more accurate than the crusher method why not just measure and post the pressure of the (then) existing loads for the standard pressure?
Why reduce the pressure standard unless there was a problem with existing loads? If testing with the transducer and finding the loads were overpressure, why not leave the pressure limits alone and lower the recommended powder charge weights?
Seems to me the pressure limits were lowered for some other reason.

CraigC
December 26, 2012, 04:14 PM
However, when they tried the same thing with non jacketed bullets, forcing cone failure appeared and fairly quickly, which was apparently caused by lead deposits in the cones causing pressure on the cone to fracture them.
This is total BS from somebody who admits to never using a cast bullet. If you match your diameter and hardness to your sixgun and velocity range, there is no leading. However, use the wrong size/hardness bullet and you will get leading. Shoot tens of thousands of rounds through a continually leaded bore and I wouldn't be surprised to see some issues crop up. But some people get weird ideas about cast bullets in their head and there's no convincing them otherwise.

Steve C
December 26, 2012, 04:45 PM
The change in measuring scale came in the late 60's...not 1995.

That was a political change. Not scientific.

If there was any change in the 60's it didn't come to light in any of the loading manual publications until the 80's. All my old manuals from the early 70's and most from the 80's quote pressures in CUP's for rifles and handguns and LUP's for shotguns.

Remember that SAAMI is not a governmental agency but a trade organization of arms and ammunition manufacturers. Politics has little to do with their publications of pressure guidelines in the manufacturing of ammunition.

nofishbob
December 26, 2012, 04:51 PM
Steve, I wonder if the politics mentioned were intended to be the politics between manufacturers within their trade association

Bob

Blue Brick
December 26, 2012, 08:18 PM
46,000 cup in 1981

Jaywalker
December 27, 2012, 09:27 AM
Showmebob, I think all of us wish SAAMI had tested and published equivalent loads using multiple methods, but if they did I'm not aware of it. It sounds like economics and policy, from my experience in corporations. No one wants to repeat a standard test because different results cause confusion. "What should we do? Issue a changed standard?" If it comes out the same, you've just wasted time and crushed another copper cylinder. Too bad, though.

Here's an interesting wiki on CUP: https://en.wikipedia.org/wiki/Copper_units_of_pressure
They make an informative point, "Since a longer duration, lower pressure pulse can crush the cylinder as much as a shorter duration, higher pressure pulse, CUP and LUP pressures frequently register lower than actual peak pressures (as measured by a transducer) by up to 20%."

For those who visit that wiki site, note in the references at the bottom a nice paper reference written in 2002, "Correlating PSI and CUP," by Denton Bramwell. In it he finds CUP and PSI "correlated," but not "equivalent," with a good example for the difference being his increasing weight compared to his belt size - as one gets bigger so does the other, but it's hard to say by how much.

It's clear the use of piezo/strain gauges found higher peak pressures in common loads and so they dialed them back. Why they dialed them back, however, is conjecture, based on your social views, e.g., nasty lawyers, need to keep K-frames running, various conspiracies, real concern for customers, etc. I do note that Smith makes the 357 currently in J-, L-, and N-Frames, but not K, for what it's worth.

I do wish we had the earlier standard to compare, though.

showmebob
December 27, 2012, 12:37 PM
Jaywalker

Thanks for the info. I read and re-read it.

Maybe I'm way off this morning as sleep evaded me last night but here's my take for whats its worth.

If a gun was built to withstand xxx pressure and that pressure was then checked with a transducer and found to be higher than xxx (and the guns were experiencing no failures) then the guns were built to acually withstand xxx+ pressures. Therefore the pressure standards could (and maybe should) have been actually raised to the pressure readings obtained with the transducer. Since the pressure standards were lowered the pressure standard must have been reduced due to gun failures/desires to build lighter guns etc, not due to the accurate transducer readings.

At least this is the way I'm thinking this morning. All thoughts appreciated.

Jaywalker
December 27, 2012, 02:26 PM
I'm not an engineer or a metallurgist, but here's my take on engineering/production thinking: you pick steel and processes (forged, cast, machined, etc.) based on expected load, both for individual and cumulative lifetime use), then add in some safety percentage in case you're wrong about the load - a 50% safety margin, for example (just for argument, not even a guess), over the requirement. PSI testing was not available widely until the mid-1960s, so I suspect the engineers at the time created an equivalency between the PSI design characteristics of steel and the LUP/CUP testing methods since direct PSI testing on barrels wasn't available. If you're reputable, you build it so it doesn't explode, and since we have few kabooms, relatively, Smith is by definition reputable.

While in the case of our 357 example they appear to have been safe instantaneously (no disastrous failures), the more accurately-measured pressures were probably above the basic design requirement and were well into the safety margin to the extent they lessened revolver's lifetime below that particular design parameter. It turned out that CUP/LUP and PSI were not directly equivalent, so something had to change - stronger steel, redesign, or lower pressure. (If the J-frame has less steel, maybe they assumed few people would want to shoot full house loads - I have no opinion.) Smith did introduce the L-frames, then, so they did make use of at least two of the three alternatives.

I had both a Smith Model 19 and a Model 66 and neither broke, but the problems with that model using 125 gr loads is very real and is documented extensively elsewhere. A problem seemed to be the necessity of milling a flat on the bottom of the facing cone - it was a problem, even when the remaining forcing cone is larger than the original, fully round forcing cone on the J-frame 357. So, I guess what I'm saying is there were pressure problems with your "xxx" load example, and the solution is what we have today.

That's not to say that Smith drove this particular decision or that it was based on any K-frame problems, but as Smith & Wesson's a part of SAAMI industry group, they would have to have agreed with the need to reduce pressure or it might not have happened.

You asked for thoughts, but while I have somewhat of a background in production, I'm not an engineer or metallurgist, so if one signs on, I'll defer to him/her for a better explanation. I'm speculating on motivations of a company and engineers from years ago, so I've almost erased this post several times now as it comes close to too many I've read on the internet that have no basis in fact - I'm just stringing together the few things I know. I still may erase it.

On another issue, has anyone noted that this thread now has over 143,000 page views?

murf
December 27, 2012, 02:41 PM
jaywalker,

go to "sammi.org" under "info and specs" you will find the ansi standards that came out in 1993. their charts show both copper crusher and piezo electric transducer pressure data for the same test ammo. so, you can compare the two.

fyi, i think there are 11 kinds of people: those who understand internal ballistics, those who don't, and those who have never been exposed (ignorant).

murf

Jaywalker
December 27, 2012, 05:59 PM
Thanks, murf, it was there and I just didn't see it CUP and PSI compared. You wouldn't happen to have the pre-1993 standards, too, would you?

murf
December 27, 2012, 10:29 PM
not from sammi. i get all my pre-1993 pressure data from the speer reloading manual number eleven (was going to type 11, but thought it might confuse someone).

the max pressures (in c.u.p.) are in each of the cartridge info page.

murf

Jaywalker
December 28, 2012, 07:26 AM
Can you list a couple of the pre-93 pressures that approximate factory, please?

I generally get rid of my older reloading manuals when I get new ones, but I did keep my Speer Number 3 from 1959. There's no pressure listed in it, and only cast bullets for handguns. (I was a little young to reload but I used this manual when I started a few years later with a 1917 Colt.)

ArchAngelCD
December 28, 2012, 10:15 AM
I'm not following the "change in testing methods" argument. Even if changing over to piezo electric testing showed pressures were higher than when testing with copper crush method of testing why would that trigger lowering the pressures? I could understand lowering the powder charges to lower the pressures read by piezo electric testing down to where they should be but why would you need to lower the limits? :confused:

murf
December 28, 2012, 03:39 PM
jaywalker,

it would be easier for you to give me a cartridge, or a list, first.

archangelcd,

who knows what goes on in the minds of men. i'm sure they had their reasons: political, most likely. can you say 40 s&w and 357 sig (over did it with the 10mm)?

the only two rifle cartridges with a drop in max pressure: 270 win and 222 remington. all others stayed the same. go figure!

murf

rcmodel
December 28, 2012, 03:53 PM
Except they started calling the standard pressure .257 Roberts +P though.

rc

murf
December 28, 2012, 04:20 PM
the standard pressure for the 257 roberts has always been 45,000 psi (they did not use the "c.u.p." designation back then). this is per the speer number 11 manual.

the 257 roberts+p pressure is 50,000 c.u.p. the 257 roberts pressure is 45,000 c.u.p. this is per the sammi voluntary performance standards of 1993.

murf

Jaywalker
December 28, 2012, 05:52 PM
I'm not following the "change in testing methods" argument. Even if changing over to piezo electric testing showed pressures were higher than when testing with copper crush method of testing why would that trigger lowering the pressures? I could understand lowering the powder charges to lower the pressures read by piezo electric testing down to where they should be but why would you need to lower the limits?
ArchAngelCD,
SAAMI is an industry association and members all agree to abide by the pressure limits set. This allows gunmakers to know what pressures to build firearms to and us to be sure the cartridge we've bought won't be either a squib or a bomb when we squeeze the trigger. SAAMI serves as a clearinghouse for industry's wishes, not a governing body, so once industry has decided, SAAMi publishes a new standard and members (and probably others) load their cartridges to it.

murf,
Just the pre-1993 standard pressure for the 357, please, if you have it. I've read anything from 45,000 to 47,000 cup.

Clark
December 29, 2012, 04:34 AM
https://groups.google.com/forum/?hl=en&fromgroups=#!msg/rec.guns/S_dalM1NJe0/cBSU4bR2jz8J

2. John Bercovitz Feb 11 1993, 5:48 pm
Newsgroups: rec.guns
From: ber...@bevsun.bev.lbl.gov (John Bercovitz)
Date: 12 Feb 93 00:48:39 GMT
Local: Thurs, Feb 11 1993 5:48 pm
Subject: Re: Brass Expansion in a .357
Reply to author | Forward | Print | Individual message | Show original | Report this message | Find messages by this author
In article <JANECZKO.93Feb10123...@csd630a.erim.org> janec...@csd630a.erim.org
(Mike Janeczko) writes:

#....... Also, some postings ago,
#suggested that the thickness of the metal used for the cylinder has something
#to do with it. Next time I see the guns, I'll compare.

Sheesh! I can tell _I'm_ not a very convincing poster! 8-)
OK, here's something I posted a long time ago after I did
some figuring for a friend of mine. It's a little broader
than your question but the answer to your question is imbedded.

John Bercovitz (JHBercov...@lbl.gov)

--------------------------------------------------------------------------

A friend asked why steel cases aren't more common since they would
allow higher chamber pressures. I thought that as long as I had
written something up for him, I might as well post it here:

Material Properties
CDA 260 cartridge brass: barrel steels:
Young's modulus = 16*10^6 psi Young's modulus = 29*10^6 psi
Yield stress = 63,000 psi min. Yield stress: usually > 100,000 psi

I was going to get back to you and explain further why brass is a better
cartridge case material than steel or aluminum. Sorry I took so long. I
left you with the nebulous comment that brass was "stretchier" and would
spring back more so it was easier to extract from the chamber after firing.
Now I'll attempt to show why this is true given the basic material properties
listed above.

A synopsis would be that the propellant pressure expands the diameter of
the thin wall of the cartridge case until it contacts the interior wall
of the chamber and thereafter it expands the case and the chamber
together. The expansion of the cartridge case, however, is not elastic.
The case is enough smaller in diameter than the chamber that it has to
_yield_ to expand to chamber diameter. After the pressure is relieved by
the departure of the bullet, both the chamber and the cartridge case
contract elastically. It is highly desirable that the cartridge case
contract more than the chamber so that the case may be extracted with a
minimum of effort.

A quick review of the Young's modulus: this is sort of the "spring
constant" of a material; it is the inverse of how much a unit chunk of
material stretches under a unit load. Its units are stress / strain =
psi/(inch/inch). Here's a basic example of its use: If you have a 2
inch by 2 inch square bar of steel which is 10 inches long and you put a
10,000 pound load on it, how much does it stretch? First of all, the
stress on the steel is 10,000/(2*2) = 2500 psi. The strain per inch will
be 2500 psi/29*10^6 = 0.000086 inches/inch. So the stretch of a 10 inch
long bar under this load will be 10 * 0.000086 = 0.00086 inches or a
little less than 1/1000 inch.

Yield stress (aka yield strength) is the load per unit area at which a
material starts to yield or take a permanent set (git bint). It's not
an exact number because materials often start to yield slightly and then
go gradually into full-scale yield. But the transition is fast enough
to give us a useful number.

So how far can you stretch CDA 260 cartridge brass before it takes a
permanent set? That would be yield stress divided by Young's modulus:
63,000 psi/16*10^6 psi/(inch/inch) = .004 inches/inch.

How far can you stretch cheap steel? Try A36 structural steel:
36,000 psi/29*10^6 psi/(inch/inch) = .001 inches/inch.
How about good steel of modest cost such as C1118?
77,000 psi/29*10^6 psi/(inch/inch) = .003 inches/inch.
(Note that C1118 doesn't have anywhere near the formability of CDA 260.
Brass cases are made by the cheap forming process called "drawing"
while C1118 is a machinable steel, suitable for the more expensive machining
processes such as turning and milling.)

What about something that's expensive such as CDA 172 beryllium copper?
175,000 psi/19*10^6 psi/(inch/inch) = .009 inches/inch.
(This isn't serious because CDA 172 is pretty brittle when it's _this_
hard.)

Titanium Ti-6AL-4V
150,000 psi/16.5*10^6 psi/(inch/inch) = .009 inches/inch
(This is an excellent material though expensive and hard to work with.)

Really expensive aluminum, 7075-T6
73,000 psi/10.4*10^6 psi/(inch/inch) = .007 inches/inch
Cheap aluminum, 3003 H18
29,000 psi/10*10^6 psi/(inch/inch) = .003 inches/inch
(Aluminum isn't a really good material because it isn't strong and cheap
at the same time, it hasn't much fatigue strength, and it won't go over
its yield stress very often without breaking. So you can't reload it.
It makes a "one-shot" case at best. Also, 7075 is a machinable rather
than a formable aluminum, primarily.)

Magnesium, AZ80A-T5
50,000/6.5*10^6 = .0077
(Impact strength and ductility are low. Corrodes easily.)

+Here's the important part: Even if you stretch something until it
+yields, it still springs back some distance. In fact, the springback
+amount is the same as if you had just barely taken the thing up to its
+yield stress. This is because when you stretch it, you establish a new
length for it, and since you are holding it at the yield stress (at
least until you release the load) it will spring back the distance
associated with that yield stress. So the figures given above such as
.004 inches/inch are the figures that tell us how much a case springs
back after firing.

Changing subjects for a moment: How much does the steel chamber expand
and contract during a firing? Naturally this amount is partially
determined by the chamber wall's thickness. The outside diameter of a
rifle chamber is about 2 1/2 times the maximum inside diameter,
typically. The inside diameter is around .48 inches at its largest.
Actual chamber pressures of high pressure rounds will run 60,000 psi or
even 70,000 psi range if you're not careful.

One of the best reference books on the subject is "Formulas for Stress
and Strain" by Roark and Young, published by MacGraw-Hill. Everyone
just calls it "Roark's". In the 5th edition, example numbers 1a & 1b,
page 504, I find the following:

For an uncapped vessel:
Delta b = (q*b/E)*{[(a^2+b^2)/(a^2-b^2)] + Nu}

For a capped vessel:
Delta b = (q*b/E)*{[a^2(1+Nu)+b^2(1-2Nu)]/(a^2-b^2)}

Where:
a = the external radius of the vessel = 0.6 inch
b = the internal radius of the vessel = .24 inch
q = internal pressure of fluid in vessel = 70,000 psi
E = Young's modulus = 29 * 10^6 psi for barrel steel
Nu = Poisson's ratio = 0.3 for steel (and most other materials)

A rifle's chamber is capped at one end and open at the other but really
it's not too open at the other end because the case is usually bottle-
necked. You'd have to go back to basics instead of using cookbook
formulae if you wanted the exact picture, but if we compute the results
of both formulas, the truth must lie between them but closer to the
capped vessel.

For an uncapped vessel:
D b = (70000*.24/29*10^6)*{[(.6^2+.24^2)/(.6^2-.24^2)] + .3} = .00097

For a capped vessel:
D b = (70000*.24/29*10^6)*{[.6^2(1.3)+.24^2(.4)]/(.6^2-.24^2)} = .00094

There's not a whole heck of a lot of difference between the two results
so let's just say that the chamber's expansion is .001 inch radial or
.002 inch diametral.

The cartridge case's outside diameter is equal to about .48 inch after
the cartridge has been fired. So its springback, if made from CDA 260,
is .004 inches/inch (from above) * .48 inch = .002 inches diametral
which of course is just the amount the chamber contracted so we've just
barely got an extractable case when chamber pressures hit 70,000 psi in
this barrel. This is why the ease with which a case can be extracted
from a chamber is such a good clue as to when you are reaching maximum
allowable pressures. By the same token, you can see that if a chamber's
walls are particularly thin, it will be hard to extract cases (regardless
of whether or not these thin chamber walls are within their stress limits).
A really good illustration of this can be found when comparing the S&W
model 19 to the S&W model 27. Both guns are 357 magnum caliber and both
can take full-pressure loads without bursting. The model 27 has thick
chamber walls and the model 19 has thin chamber walls. Cartridge cases
which contained full-pressure loads are easily extracted from a model 27
but they have to be pounded out of a model 19. So manufacturers don't
manufacture full-pressure loads for the 357 magnums anymore. 8-(

We can see from the above calculations that a steel case wouldn't be a
good idea for a gun operating at 70,000 psi with the given 2.5:1 OD/ID
chamber wall ratio if reasonable extraction force is a criterion. Lower
pressures and/or thicker chamber walls could allow the use of steel cases.
jb


I was so impressed with this 1993 post that in 2005 I tapped John to help me prove the load books were wrong about the CZ52 vs the Tokarev strength.

I sent him ~ a dozen CZ52 barrels and he tested them for RC hardness at JPL.

Jaywalker
December 29, 2012, 10:35 AM
Clark,

That's interesting. Can we assume from that that the J-frame 357's five-shot cylinder allows for greater cylinder wall thickness than the six-shot cylinders of the old Models 19/66?

Clark
December 29, 2012, 11:25 AM
Jaywalker,

Model 60 J frame 5 shot 38 sp I reamed out to 357 mag:
.058" to the outside
.108" between chambers
1.308" cylinder diameter
1.535" long cylinder
.250" x.090" slots in cylinder for bolt

Model 66 K frame 6 shot 357 mag:
.084" to the outside
.075" between chambers
1.456" cylinder diameter
1.675" long cylinder
.275" x.105" slots in cylinder for bolt

The 357 mag cartridge could be 1.59 long and the rim could be as short as .049" so the cylinder should be at least 1.541" long

I have blown up enough cylinders on 38 specials and 32 S&W Longs to know that both the between cylinders AND the to outside thickness must both break. That would mean they add for strength, like ropes in parallel.

J frame = .164" sum for strength calc
K frame = .159" sum for strength calc

It is going to be real hard to blow up either. What happens with smiths is that the slots in the cylinder or the slot in the frame get sloppy. That makes the cylinder loose like a Ruger in rotation, not tight like a post 1907 Colt. The S&W model 29 44 mag got bigger slots in later dash numbers to beef it up.

Jaywalker
December 29, 2012, 11:45 AM
Clark,

Just to be clear, are those measurements to the outside of the cylinder the maximum measurements, or do they include the cylinder stop slots? It appears to me the M19/66 has the slots over the chamber proper, while the J seems to offset to thicker metal.

murf
December 29, 2012, 12:22 PM
jaywalker, for the 357 magnum:

old - 46,000 c.u.p.

new - 45,000 c.u.p.

new p.s.i. - 35,000

murf

Clark
December 29, 2012, 12:45 PM
Jaywalker,
You are right, I was measuring from the chamber to the major OD of the cylinder.

I never noticed it before, but the 5 shot geometry does not have the slot over the a chamber. The slots are between the chambers. 6 shot cylinders have the slot weakening the chamber. That is an advantage for 5 shot strength.

CraigC
December 29, 2012, 01:35 PM
I don't think you can ascertain a cylinder's strength by measurements alone. Particularly if you are not taking into account the location of the bolt notch in relation to the chambers. Because this is almost always the weakest point.

Clark
December 29, 2012, 02:08 PM
CraigC
I could do a thin wall formula for stress, and maybe a Lame's formula for thick wall, but to do it right you would need one of Roark's open end tube formulas. In all three the stress goes up proportional to the inside diameter.

So at the cave man level, I have tried to blow up many guns.

I don't care if the gun is 150 years old or new, unless it is a Ruger 454 made of specialty steel, this is my guideline for 3/8" to 1/2" inside diameters:
.100" thick, I can't blow it up.
.050" thick, blowing up is easy.

I bought a 90 year old 32-20 revolver Thursday. It is .136" between and .120" to the outside. The inside dia is .356"

SAAMI is 16kcup.
I have not shot it yet, but...
I can tell by looking at it that in a work up it will pierce a CCI450 small magnum rifle primer [the toughest I have found] before it will burst the chamber.
That should be 80 or 90k.

Jaywalker
December 29, 2012, 02:13 PM
Clark,
Well, if I read John Bercovitz's formulae right, the M19/M66 cylinder slot cuts are less a yield strength issue than a Young's Modulus inconvenience. It probably only added to the extraction issue he already noted. The numbers don't lie, though - the K-frame cylinders aren't as strong as the J-frame. I'd read about the K forcing cone problems, but this one is new to me. Thanks.

murf,
Thanks. Only a 1,000 cup, then. I would think we'd get that much variance from how deeply we seat or crimp, or how hot the day is. Hardly seems worth the effort. I appreciate your looking.

CraigC
December 29, 2012, 02:24 PM
So there is no consideration of the alloy used or its heat treatment??? This is a dangerous game you're playing and I hope everybody reading this thread understands that.

Deer_Freak
December 29, 2012, 02:45 PM
I am glad all these problems apply to S&W. I have seen people use ruger only charts, then add a little more. The only thing that happened is the gas check failed (in the bullets we were able to recover). I realize that the gas check failing causes leading and in time a loss of accuracy. But nothing happened that would cause a catastrophic failure.

I have only seen people do this with cast bullets. I have no idea what, if anything would happen to a jacketed bullet.

Jaywalker
December 29, 2012, 04:37 PM
CraigC: http://www.engineeringtoolbox.com/young-modulus-d_417.html

Sorry, posted before I finished. Clark is much more qualified than I am to respond to this, but pending his response, here's my quick take:

Young's Modulus is just a ratio, and it applies to many material, not just steel, as shown on the linked page. As far as alloy of steel goes, it just doesn't make much difference. It might be a small number followed by 6 zeroes, so you're dividing some number by 25,000,000, 29,000,000, or 35,000,000. The difference is nearly too small to measure, and not enough to worry about in revolver cylinders.

I'd be interested read Clark's take on heat treating, but if anything I would expect it to improve the situation.

Clark
December 29, 2012, 05:50 PM
Oi, am I not qualified. I inherited gun design books, but not gun design brains. I designed electronics. Some gun electronics, but not the gun. I modify guns for fun.

They don't do much heat treat on revolver cylinders, usually.

All the 38 specials I reamed out to 357 mag were soft.

If you try to make a gun, you want some heat treat so it can be light. But hard metal is not easy to machine. And heat treating after machining can be a problem with warpage.

So there is a trade off. .. except the Ruger 454 that they just wanted to ream out a 44 mag design paper thin and then have really high proof loads. They split cylinders and blew out forcing cones until they found a specialty stainless steel that was economical to machine and strong too.

Most of the time over the last century when making revolvers, they took something like 4140 steel that would be RB86 80ksi fully annealed, but they buy it hardened to RC29 132 ksi tensile strength.

Put RC29 4140 in your lathe or mill and it machines ok with coolant all over it. If you ever let a spot get hot, the steel turns very hard and wrecks your tool Then you must try to cut out the hard spot with carbide.

4140 can be hardened to ~RC60 ~ 300 ksi strength, but that is not your firearms chamber. My father called out 4140 in coil springs for gun designs. I think some chisels are made of it. So in other applications 4140 is very hard. But not in revolver cylinders.

WardenWolf
December 30, 2012, 04:10 AM
Ruger has been the true king of revolvers for many years now. Smith & Wesson is largely stuck in the past, and hasn't improved anything beyond their triggers. Their standardized frame system leaves no room for major innovation, as anything new they make has to fall within dimensions that were defined more than half a century ago. Other manufacturers are free to innovate at will, and come up with completely new designs as needed. Only Smith & Wesson has shot themselves in the foot this way.

Clark
December 30, 2012, 12:44 PM
WardenWolf,
I am nobody in the world of revolvers. My father did design a 115mm six shooter for the marines in 1960, the XM-70. "X" means experimental, and we never got much money. The patent on his 6 shot revolver
http://www.freepatentsonline.com/4353285.pdf
That patent does publish the formula for parabolic taper hydraulic recoil, that before he did the math on his M55 design, the tapers were determined empirically since the French invented it in WWI.
Anyway, I own ~ ~ 50 revolvers, mostly bought for testing.
~10 years ago I got (5) Colt Police Positive revolvers as police surplus for destructive test. I was really shocked by the quality of the design. I could not shoot them loose.
I bought a Ruger blackhawk ~5 years ago and fired one shot. I was impressed negatively. I have not pulled it out of storage since. I also have a security six, which seems like a better gun.
I don't doubt that Ruger revolvers might take over the world, but this nobody likes Colts.
There is a poster on the firing line that makes amazingly good posts about gunsmithing almost all guns. He was a trained watchmaker before he became a gunsmith.
Dfariswheel May 9, 2001, 03:24 AM
Posts: 6,394
Colt was always seen as the Rolls Royce of handguns. Colt spread their dollar around on the gun, pretty equally on the outside finish, and the inside. Smith & Wesson spent their's on the outside, with a great blue job.
I think if you research the posts made by Dfariswheel, you will see HE is intrinsically somebody.

ArchAngelCD
December 30, 2012, 07:21 PM
Ruger has been the true king of revolvers for many years now. Smith & Wesson is largely stuck in the past, and hasn't improved anything beyond their triggers. Their standardized frame system leaves no room for major innovation, as anything new they make has to fall within dimensions that were defined more than half a century ago. Other manufacturers are free to innovate at will, and come up with completely new designs as needed. Only Smith & Wesson has shot themselves in the foot this way.
I'm very confused as to what you are talking about? Not that I care what anyone thinks about S&W but what you said confused me. S&W has come out with the X frame which is different than the others. They also developed the Bodyguard 38 which is completely different than any other revolver ever made for several reasons. It also has an integral laser which is different too. They were also the first to make 7 and 8 round centerfire revolvers. Please clear up what you meant, I'm curious...

WardenWolf
December 30, 2012, 09:46 PM
S&W is finally starting to produce new stuff, but most of their offerings are still based on their old-fashioned standardized frame system. For too long they were afraid of breaking the system. On the other hand, you look at companies like Ruger that will create a completely new design as needed, and you see the intrinsic difference. With other companies, you see specialized designs, for a particular role. With Smith & Wesson, you see minor rehashes of the same thing, when a completely new design is often called for.

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