Strength of early 20th century rifles.

[wiljen]

We often hear (whether correctly or not) that one of the reasons that top loads in manuals have decreased over the years is improvements in pressure testing equipment. The implication is that in the early 1900s, we could not adequately test pressure so many an over-pressure load was published and used.

Why do we never hear about the flip-side to this argument? Doesn't it stand to reason that if all the ammo loaded for WW I for a particular arm was over-pressure, and it was used for several years in great quantities by the combatants, that the arms would have proven the load was too hot then were it a problem?

I'm not recommending that we start loading things hotter, I'm wondering when the last time someone really did full scale pressure tests on actions was. Wouldn't it be interesting to see what they rate using today's equipment?

Knowing that it has been most of 35 years since a truly NEW action has been developed, it seems entirely likely to me that Winchester 70s haven't been re-tested since the 1964 change over, likewise Remington 700s have remained unaltered since when?

Knowing that these tests would cost the manufacturer and the return would only create a new set of issues, (Nothing like reading the ammo box warnings "Only to be used in the following guns built on or after..."), have the manufacturers simply accepted the now aging SAAMI standards as gospel more as a matter of ease than of correctness as it regards modern test methods and steels?

I think we can all agree that in some cases, the standards are there in deference to those older arms and they could be safely increased in modern guns. (We've seen such in the 45-70 and could see such in the 30-06 considering its stable mates the 270 and 280 both operate at higher pressures).

Having seen many 03s and 17s converted to 270, 280, and even belted magnums at higher pressures got me to thinking. If the tools that we used to measure action strength were equally poor when compared to the tools we used to measure the pressure a load created, are we assuming the data needs to be reduced when in fact we are basing that assumption on equally flawed data?

[Char-Gar]

The weak link in the chain is the brass cartridge case.

[Multigunner]

One major flaw in the previous attempts at testing actions to destruction has been the belief that plugging the bore would give an accurate measure of action strenght vs barrel strenght.

If the barrel splits or breaks off at point of obstruction before the action fails or even shows damage, the calculated pressure at point of failure is not the level of pressure on the locking lugs themselves.
This was discovered during development of the rod type rifle grenades. It was also noted during early blow up tests of the Lee Enfield rifles.
It may take 100,000 PSI to burst or snap off a barrel at point of obstruction but the pressure on the locking lugs is not 100,000 PSI at that moment in time. Its higher than normal, but if the barrel breaks as it normally does, the pressure is relieved before the pressure wave fully reaches the chamber and boltface.
A barrel with much greater than normal strength might hold the pressure until the pressure wave recoils into the breech, but few mil spec barrels are that tough.

This applies to the early smokeless powder military rifles only, I don't know how BP or heavy barrel modern sporting rifles would react.

While much milspec ammunition of WW1 proved defective it was seldom due to being overloaded. Extreme high pressures were more often due to accelerated degradation of the propellent due to rushed production.
Major cause of action failures was cartridge case head failure, which was more often than not due to defective brass or drawing technique rather than high pressures.

While the crusher gun and tarage table methods of measuring pressure are not the best, they were and are still used and at least give a good point for comparasions.

Another factor is simple metal fatigue. Some late 19th-early 20th century rifles were manufactured from fairly advanced alloys, others were not.
Alloying agents that reduced the affects of metal fatigue were used for some alloys, mainly through the work of metallurgists who were tasked with creating metals that increased the safety and durability of steam engines, both locomotive and steamships, and the axles and suspensions of rolling stock. The flegling automobile industry did its part as well.

A rifle might look as good as new on the outside, yet have been subjected to degraded or unsuitable ammunition for decades. Headspace issues are a warning sign, but a rebarreled rifle might have excellent headspace and bore, yet the action have been on its last legs before refurbishment.

Military rifles were designed to have a wide margin of safety, but one should not intrude into that margin of safety by increasing chamber pressure levels beyond that recommended when the rifles were new.

[wiljen]

The weak link in the chain is the brass cartridge case.

always heard that too. Don't think it universally holds water either. Never heard of them beefing up the 30-06 brass to make 270 cases for example.

Mind you, it may be perfectly true in some cases. I just think we take a lot as universal gospel without ever really asking or knowing.

[Larry Gibson]

Wiljen

In the case of the '06 and the '03 it was defective cases made during WWI war ammunition production that was the problem, not "over-pressure load(s) was published and used". Not sure that's what you were hinting at but the LSN '03 are the most discussed in that regard.

I agree the case being the weak point only holds when very unsafe psi levels are reached. Over the years I've seen and loaded '06 cases in one form or another to 62 - 65,000 psi (measured).

Larry Gibson

[wiljen]

No, I knew the low serial number 03s had issues with heat treatment and that some of the early 06 cases were bad as well. I wasn't really thinking of those at all. More thinking about the somewhat arbitrary nature by which maximum working pressures seem to have been set over the years. The 30-06, 280, and 35 whelen all share the same standard, but the 270 and 338-06 share a higher one. Several other examples exist where pressures change between rounds usually chambered in the same guns and with the same parent cartridges.

I just think it odd that we say our pressure testing methods have improved, steels have improved, but shouldn't our methods of testing those steels have benefited from the same advancements.

I suspect that most of those tests were never re-run simply because the expense made them less than desirable when no direct benefit was available to the makers. These were old guns that had long since served their purpose, thus no real impetus for doing the work.

[higgins]

If manufacturers did retest their actions I don't think we would see the results, and I don't blame them. If it was found that action xyz would endure 100k psi pressure, we all know that a few handloaders would start routinely overloading their rifles, to the point of failure. They wouldn't understand some basics like the fact that not all xyz actions may hold up to gross overloads regardless when it was made, internal flaws they might have, or the fact that Uncle Bill drilled the action full of holes in abortive scope mounting efforts, etc. For all we know, manufacturers may have already done these tests so that they can defend themselves against lawsuits for "faulty" actions.

[Char-Gar]

Guys.. I should have been more clear. Cartridge brass will fail due to pressure sooner than almost all gun steel. If a case never fails, then the issue of rifle strength never becomes and issue. The rifles does not fail until AFTER the brass has failed.

[Multigunner]

Guys.. I should have been more clear. Cartridge brass will fail due to pressure sooner than almost all gun steel. If a case never fails, then the issue of rifle strength never becomes and issue. The rifles does not fail until AFTER the brass has failed.
Generally true but not always.
Standard cartridge case brass will begin to cold flow at 65,000 CUP-85,000 PSI, some older actions may not hold up to pressures a good deal below that.

The cases used for proof testing are generally of tougher, or at least thicker brass.
Some were capable of holding at 125,000 CUP.

Then headspace raises its ugly head.
Military spec cases intended to withstand use in machineguns as well as rifles has a thicker web than almost any commercial sporting rifle brass.

A military rifle might withstand an increase in headspace of up to .03 and a quality milspec cartridge case may not rupture under normal pressures. The same loading in the same rifle with an average commercial cartridge case would almost certainly cause a failure of the case walls and/or casehead.
A longitudinal split in the unsupported case wall can initiate a split in the case head.

Bottle neck cases have some taper to the case body. When headspace reaches dangerous limits the tapered case is no longer a proper fit in the tapered chamber. Clearance increases with headspace.
Any irregularity in the chamber wall greatly increases the danger.

Another source of failure is due to a manufacturing shortcut used in barrel manufacture.
To cut costs and machinng time undersized barrel blanks were bumped up to form an increased diameter breech section.
If heated to a too high temperature during this process the breech area could be weakened and could sooner or later form longitudinal cracks in the chamber area.
When a barrel splits at the chamber it excercizes great force on the receiver ring usually spliting the ring as well.
If the ring holds the barrel can split lenghtwise from chamber fowards.

[wiljen]

Point taken Chargar. I had assumed it was the age old 45 Colt brass is weaker than 44 mag brass kind of argument. having cut 357s back to 38 length and weighed them, I know there is little to no difference in those and I suspect most brass has roughly the same strength within design familys.

[Ed in North Texas]

With regard to the reduction of powder charge due to improved pressure testing capabilities, it isn't the actions which have been re-tested, but rather the loads listed in reloading manuals. Improved testing equipment and methods revealed significantly higher pressures than previously reported.

As for test actions to destruction, some of us will remember the HP White lab destruction testing of handguns, at the behest of the government, to come up with a standard with which to determine what was, and was not, a "Saturday Night Special". IIRC, the testing regimen for the revolvers in the test was one (or more) full cylinder of "normal" ammunition, followed by a full cylinder of "proof" ammo. Then another course of regular ammo, followed by proof + (10 or 25)% increased over "proof" loads, then more regular, etc. Some of the expensive revolvers (e.g. Colt sticks in my mind) failed earlier than the inexpensive revolvers. IIRC the testing ended with some of the revolvers not being destroyed, and most of the failures were for minor parts. I seem to remember a S&W .357 managed a cylinder full of ammo which produced 125,000 PSI (I'm pretty sure of the caliber and PSI, though it could have been 145,000 - less sure of the brand of revolver). They couldn't get any more of any type of powder in the case to go higher. That was a long time ago, somewhere around 1972.

[Rio Grande]

I've worked in machine shops over 35 years. I very much suspect that good Swedish steel made 100+ years ago is superior to modern Chinese, Indian, and Pakistani steel we are buying and using today.
And the level of workmanship we see in those 100+ year old rifles! U.S., Swedish, German, English...any European-made rifle of those days. To see in particular an old Swedish Mauser or a U.S. Springfield...made with belt-driven lathes and mills and non-carbide tools...it's just incredible to see the quality of machine work, polish and bluing.
And this on mass-produced rifles! Computer controls? Those guys didn't even have pocket calculators!
We can do that again, even better products and quality with todays technology. All the worker needs are the tools...and the commitment to quality from the front office.

[Multigunner]

Point taken Chargar. I had assumed it was the age old 45 Colt brass is weaker than 44 mag brass kind of argument. having cut 357s back to 38 length and weighed them, I know there is little to no difference in those and I suspect most brass has roughly the same strength within design familys.

That was partly due to the old style balloon head cases. When they switched to solid head cases the powder capacity was reduced, so they actually ended up having to downlod the .45 Colt a bit to stay within the safety margin of the older BP frames.

Personally I always figured the screw type cylinder catch (?) took away less meat from the front of the frame.
I've had to pound a few cheaper revolver frames back into shape after decades of cylinder slap had pushed the front of the frame out a few thousandths (more like several hundreths) to much. On some you could see that the breech of the barrel was now at an angle to the cylinder face, the barrel angled up a few degrees by the bowed frame.
Haven't seen that on a Colt yet though.


The balloon head case reminds me of something.
Winchester used a "semi balloon head" case for their .308/7.62 Palma Matchgrade ammunition, to allow more effective powder capacity when a long heavy bullet was seated to the standard cartridge OAL. The base of any bullet of 175 grains or more protrudes into the powder space reducing effective capacity.

I've heard Winchester now uses the semi balloon head case for several other relatively intense cartridges to increase powder capacity.

A semi balloon head case and high intensity charge, coupled with a loose milspec chamber and generous head space could be a cause for concern. Depends on whether the case is as strong as Winchester engineers figure it to be.
These cartridges are intended for rifles built to modern SAAMI chamber and head space specs.

While catastrophic failures are extremely rare these days, most substandard rifles having long ago given up the ghost or been scrapped when headspace got beyond safe limits, and serious injuries have been uncommon even in spectacular action failures, more than a few shooters owe their eye sight to shooting glasses.
Any failure where gas escapes, often with fragments of brass, is a danger to the shooters eyes.

[NickSS]

If you read Hatchers Note book you will find complete data as to proof loads, barrel steels, heat treatment etc of the 03 Springfield. He ought to know as he had most of the tests run as well as analysis of blow ups done. Basically low number Springfields with single heat treat were marginally safe until they went into high production during WWI. The skill level of some of the newer workers doing the heat treating was not up to pre war standards and some receivers were not adequately strong and some were down right dangerous. Add to that lower quality ammo produced by some contractors and more blowups occurred. The ones made with double heat treatment that was developed to fix the problem are the strongest 03s ever made by actual test. The later nickel steel ones were not as strong but had more give before blowing up. No issues with ammo really caused the problems but may have added to it. As far as the changing data it may be that the actual test data may change due to better equipment but I believe that most of it is due to lawyers and law suits. The original load max pressure for instance of the 357 mag was 40,000 psi and today the loading manuals and sami call for something like 32,000 psi and the velocities are nowhere near what were quoted in the late 30s for it. I think this is partly due to the plethora of mini 357 mag revolvers that are so popular today. Old Elmer Keith must be spinning in his grave.

[bydand]

I should think most of the blow-ups are the result of some handloader wanting to get some "extra velocity" from his rounds. The loading tables will give you a safe load. trying to "improve it" leads to problems. We did fight World War One with low number Springfields

[Larry Gibson]

Much has to do with the way pressure is measure these days with piezo eletronic transducers and strain gauges vs the older C.U. P. (Copper Unit Pressure) method. First thing to understand is; there is no correlation between psi figures given with the C.U.P. method and with modern piezo transducers, etc. Comparing the old 40,000 "psi" C.U.P. figure to the modern peizo transducer SAAMI MAP (Maximum Average Pressure) for the .357 magnum is meaningless.

Comparing the older C.U.P. pressure figures of any other cartridges is also meaningless. C.U.P. measures only the peak pressure, Piezo transducers and strain gauges measure the time/pressure curve. C.U.P. can bedendent on the quickness of the pressure rise and the duration. The Units of measurement are now referred to differently also. C.U.P. are usually referred to as that and piezo transducer and strain guage measurements are referred to as "psi's" now.

I concur in the case of the .357 and .44 magnums they have been "dumbed down" for the smaller, lightly constructed revolvers.

Another thing to remember about old actions. The do not get "weak" simply because they are old. "Metal fatique" doesn't come into play unless the stress applied excedes the structural elasticity of the steel. In other words, if the loads used remain under the stress limit of the action it will not get "weaker" with age or use. It may wear out or for some other reason become unserviceable (neglect being the greatest cause) but not from "old age".

Larry Gibson

[frnkeore]

Larry,
Very well said.

Here is a comparitor for CUP/PSI.

Correlating PSI and CUP

Denton Bramwell

Having inherited the curiosity gene, I just can’t resist fiddling with things. And one of
the things I can’t resist fiddling with is firearms. I think I am the only kid in town that
asked for, and got, a Fabrique Scientific strain gauge system for Christmas, and promptly
stuck it on his trusty 30-06. So I suppose that it is only natural that I’d be curious about
how CUP and PSI work. That’s what this article is about.

History

The Lyman reloading manual is one of my favorites. It’s clearly written, a pleasure to
read, and it sheds some interesting light on the history of terminology in the measurement
of chamber pressure. Before about the 1960's the only measurement system we had for
chamber pressure was the copper crusher method. Up until that time, what we now call
CUP was commonly known by two different names: CUP and PSI. The two were used
practically interchangeably. Of course, this use of PSI was incorrect. It wasn't much of a
problem until piezoelectric and strain gauge systems became commonly available. These
systems, of course really do measure in PSI. When they arrived on the scene, it caused a
lot of concern and confusion. “For years, 52,000 PSI (crusher method with erroneous
designation) had been pub lished as maximum for the 270 Win. Suddenly, there were new
publications showing 65,000 PSI …as maximum.”1

If you look at any publications before about 1965, and they say that PSI and CUP are not
the same, and that you should not attempt to convert one to the other, they are talking
about the old, incorrect use of the term PSI, not the modern, correct use of PSI from
strain gauges and piezoelectric pressure meters.

What is Correlation?

If you’re on one of the reloading bulletin boards, and say that PSI (modern use) and CUP
are correlated, you’d best be wearing your asbestos underwear. There are a lot of people
that “know” that the two systems aren’t correlated, and will tell you so in no uncertain
terms. Math and physics aren’t on their side, as we shall see. I suspect that their
“knowledge” comes from old information, published to straighten out the problems that
came from incorrectly calling CUP PSI.

If two variables are correlated, you can estimate one from the other. The opposite of this
is “statistically independent”, which means that you can’t estimate one from another.
Actually, it is very hard to come up with numbers that are completely statistically
independent, or uncorrelated. Usually the question is not whether things are correlated,
but how well they are correlated. If you plot my weight vs. my belt size for the past 20
years (please don’t!), you’ll find that one variable reasonably predicts the other. My belt
size and weight, then, are correlated. They won’t be perfectly correlated, and they might
not be linearly correlated, but they will be well correlated.

1 Lyman 47th Reloading Handbook, p92


A figure of merit for correlation is the R2 value. In the simple case of linear regression,
an R2 of .8 means that 80% of the variation in one variable is “controlled” by the other,
and the remaining 20% of the variation is unaccounted for. Run regression on a pair of
columns of random numbers, and you’ll get R2 values from a fraction of a percent to a
few percent. Run it on a very precise micrometer’s reading vs. the marked values on a
set of gauge blocks spanning a couple of inches, and you’ll get something very close to
100%.

It’s a fact that two variables that are both well correlated with a third variable must be
well correlated to each other. So if the copper crusher system is well correlated with
peak chamber pressure, and the piezoelectric PSI system is well correlated with peak
chamber pressure, then CUP must be well correlated with piezoelectric PSI. It cannot be
otherwise.

All measurement systems lie, at least a little bit. Like all measurement systems, the CUP
method and the PSI method both have a certain amount of random error in them. From
published data, (Lyman manual, p91), it is easy to estimate the random error in both
systems. The bottom line is that the random error associated with the CUP system has a
standard deviation of about 2,000 PSI (correct usage), and the piezoelectric system has a
standard deviation of about 1,300 PSI.

This random variation in the measurement systems accounts for part of the puzzlement in
attempting the conversion. The 7x57 Mauser is rated 46,000 CUP, and 51,000 PSI. The
300 Savage is also rated 46,000 CUP, but 47,000 PSI. Random error in both
measurement systems accounts for this discrepancy. Because there is random error in
both measurement systems, any conversion will be approximate, rather than absolutely
precise.

While it is true that the deformation of the copper pellet in the crusher system is
influenced by all the pressure that happens during the discharge of a bullet, it is also true
that the main thing that the CUP system measures is peak chamber pressure. The
deformation that happens "off-peak" is properly regarded as measurement system error,
and it is minimal, as I will show a bit down the page.

Searching for Correlation Between PSI and CUP

Testing for this correlation is easy. All we need is a set of measurements where the same
event was measured in both systems, and we need that set of measurements to span a
large enough range that we can “see” the correlation above the random error that is
present.

Measurements taken simultaneously on several examples of a single handload would
about the worst possible choice of data sets. Careful handloaders try very hard to
minimize variation. Ideally, the pressure variation from cartridge to cartridge is zero. In
practice, the range of pressures is so small that a regression on that data would be


completely swamped by random measurement error, which is significant in both the CUP
and piezoelectric systems.

There is a much better alternative. There are cases where SAAMI has set maximum
pressures for rifles in both CUP and PSI. That data set spans a few tens of thousands of
PSI, and, assuming that SAAMI was careful in how they set the limits, it is much better
for our purpose. I have access to about 30 such data pairs, and that is enough to provide a
reasonable estimate of the conversion factor.

Cartridge ANSI CUP ANSI PSI
222 rem 46000 50000
22-250 rem 53000 65000
243 win 52000 60000
25-06 rem 53000 63000
257 roberts 45000 54000
264 win mag 54000 64000
270 win 52000 65000
280 rem 50000 60000
284 win 54000 56000
30 carbine 40000 40000
300 savage 46000 47000
300 win mag 54000 64000
30-06 springfield 50000 60000
303 british 45000 49000
30-30 win 38000 42000
308 win 52000 60000
32 win special 38000 42000
338 win mag 54000 64000
35 rem 35000 33500
375 h&h mag 53000 62000
444 marlin 44000 42000
45-70 government 28000 28000
6.5 rem mag 53000 65000
6mm rem 52000 65000
7mm express Rem 40000 45000
7mm rem mag 46000 51000
7mm SE vH 52000 61000
7x50 R 52000 61000
8mm rem mag 37000 35000
8x50R 54000 65000

Submitting the SAAMI/ANSI numbers to regression, we get this:


Analysis of Variance
Source
Regression
Error
Total
DF
1
28
29
SS
3.302E+09
258713297
3.561E+09
MS
3.302E+09 359239761
F
7.419 0
P
.000

An R2 value of .927 puts an end to all discussion about whether PSI and CUP are
correlated. They are. To prove otherwise, you would have to prove that .927 is a lot
closer to zero than it is to one, and you’d have to show that the data pattern in the graph is
much more like a shotgun pattern than it is like a straight line. An F value in the low
teens is usually enough to show statistical significance, and we have an F value of 357.4.

If two variables are well correlated, there is always a formula for converting from one to
the other. The formula for converting from CUP to PSI is shown at the top of the graph.
Since the numbers you are converting do not precisely represent actual chamber pressure,

4



5
the results you get from the conversion will not be precise. About 2/3 of the time, the
formula will land you within 3,000 PSI, so exercise appropriate caution. Also, do not
attempt to use this conversion for handguns or shotguns, or to use it outside the range
shown. We don’t yet know how the conversion works outside the data we have studied.
Let’s go through a couple of examples to show how the formula works. The formula PSI
= -17,902 + 1.516 x CUP is useful if you have data published in CUP, and want to
compare with data published in PSI, Or, if you’re like me, and have instrumented one or
more rifles with strain gauges, you might want to use published CUP data to set an
approximate limit for your loads in PSI. My lovely 6.5x55 Swede is rated at 46,000
CUP, and has no PSI rating. What should I use for a limit in PSI? Multiplying 46,000 by
1.516, and subtracting 17,902 gives me an upper limit of about 51,834 PSI. If I graduate
to a .416 Rigby, which is rated at 42,000 CUP, the same calculation gives us 45,770 PSI.
Reversing the math the 7mm Weatherby Magnum is rated at 65,000 PSI, with no
corresponding CUP number. Converting 65,000 PSI results in a stout 54,685 CUP.
For reasons unknown to me, the 223 Rem doesn’t appear in either of the data sets I have
access to. It is also statistically very different from the rest of the data.
There is also a separate European CIP standard, which uses a different procedure, and
produces different results. Data for 191 cartridges is readily available. Their curve and
10000 20000 30000 40000 50000 60000
70000
60000
50000
40000
30000
20000
10000
CIP CUP
CIP PSI
S = 584.737 R-Sq = 99.7 % R-Sq(adj) = 99.7 %
CIP PSI = -2806.88 + 1.20911 CIP CUP
Regression Plot

formula look like this:

The European CIP conversion is much more precise than the US SAAMI conversion. If
you eliminate the statistically peculiar 280 FI NE, 310 Cadet Rifle, 38-40 Win, 44-40
Win, 7x50 R, 7x75 R SE vH, 8mm Rem Mag, and the 32 Rem, all other conversions
from CUP to PSI are within about 850 PSI. The precision of the conversion, and the fact
that the same exact values pop up again and again in the residuals indicates that the
Europeans have probably actually just been using one system, and converting by linear
formula to produce the second set of numbers.

Conclusions

1. PSI (correct use) is highly correlated to CUP. Evidence: R^2 = .927 makes it
impossible to successfully argue otherwise.
2. CUP is mainly an indicator of peak chamber pressure: Evidence: The way that
piezoelectric systems are commonly used, they report purely peak chamber pressure.
The CUP system is highly correlated with the piezoelectric system. If the “off-peak”
deformation of the copper pellet were large, the correlation to the piezoelectric
system would be poor.
3. SAAMI did a pretty consistent job of setting maximum pressure limits in both
systems. Evidence: The two are highly correlated. Basically, they got pretty close to
the same answer both ways.
4. You can convert from one system of measurement to the other. Evidence:
Definition of "correlated". Basically, correlated means that you can estimate one
variable from the other. The opposite of this is "statistically independent", which
means that you can't.
5. The formula for the conversion is the one shown above. Evidence: Produces the
"least squares fit" for the two systems, and it produces an R2 of .927. You can test the
formula by plugging in any of the CUP numbers shown above. The formula will give
you back a PSI number that is close to the one shown in the table.
6. Work remains to be done in refining the SAAMI conversion. Evidence: An R2 of
92.7% is produced, leaving 7.3% of the variation to be explained. Measurement
system error probably sets the limit of the R2 that can be obtained at around 98%.
That leaves 5.3% of the variation unexplained. Perhaps someone can discover what
the unaccounted for variable is.
7. The first example of something disproves all claims that it does not exist. The
formula exists, and it works. So all claims that it does not exist cannot be true.

© 2002 Denton Bramwell

[Larry Gibson]

frnkeore

Denton gives it the "college try" and I've had his article and formula since he published them. Nice in theory but in reality it doesn't work out. In the middle of the cartridge spectrum it can be tantalizingly close. But "close" is still no "cigar".

The problem is that C.U.P. measures a deformation caused by an imact. It only can measure the maximum force generated whether of extremely short (fast burning powder) or longer (slower burning powders) time frame. It is dependant on the strength and time elapse of the impact. Using a .308W for example; A 50,000 CUP load using bullseye is going to be a lot harder on your brass and rifle than the same CUP load using 4895.

A piezo electronic transducer/ strain gauge measures the time pressure curve/sequence. You can easily see, using the same .308W loads (62,000 psi) by the way, which is the better load giving the best internal ballistics.

Denton says his conversion will not "be precise". He negates the use of handgun cartridges and shotguns....why if the conversion is possible. On the CIP side he deletes the use of statistically peculiar cartridges.....why?

Now, Denton's work is based on "paper" and I don't mean targets. I have many times computed his conversion of CUP to psi with several rifle cartridges. The end measured psi using the Oehler M43 gave only enough success to really get in trouble if I depended on the conversion. I got a healthy chuckle out of Dr Oehler one time when I mention Denton's formula. Now if there was any correlation between CUP and psi then he should know. He said there is none and if at any time there appears to be a correlation it is simply coincidence. He knows of no ballistician in the industry that believes there is any correlation what so ever. My own humble research has verified that.

Like I said, Denton gave it a good try but no cigar. If he happens to read this I could use a good Cohiba:D

Larry Gibson

[Dutchman]

"Metal fatique" doesn't come into play unless the stress applied excedes the structural elasticity of the steel. In other words, if the loads used remain under the stress limit of the action it will not get "weaker" with age or use.

http://www.epi-eng.com/mechanical_engineering_basics/mechanical_basics_contents.htm

http://www.epi-eng.com/mechanical_engineering_basics/fatigue_in_metals.htm


Long ago, engineers discovered that if you repeatedly applied and then removed a nominal load to and from a metal part (known as a "cyclic load"), the part would break after a certain number of load-unload cycles, even when the maximum cyclic stress level applied was much lower than the UTS, and in fact, much lower than the Yield Stress (UTS and YS are explained in Stress and Strain). These relationships were first published by A. Z. Wöhler in 1858.


IS FATIGUE LOADING CUMULATIVE?

It is important to realize that fatigue cycles are accumulative. Suppose a part which has been in service is removed and tested for cracks by a certified aircraft inspection station, a place where it is more likely that the subtleties of Magnaflux inspection are well-understood. Suppose the part passes the inspection, (i.e., no cracks are found) and the owner of the shaft puts it on the "good used parts" shelf.

Later, someone comes along looking for a bargain on such a part, and purchases this "inspected" part. The fact that the part has passed the inspection only proves that there are no detectable cracks RIGHT NOW. It gives no indication at all as to how many cycles remain until a crack forms. A part which has just passed a Magnaflux inspection could crack in the next 100 cycles of operation and fail in the next 10000 cycles (which at 2000 RPM, isn't very long!).

There are abundant sources of information on this subject.

http://www.firearmsid.com/Feature%20Articles/022001/HPWhite.htm

http://www.metallurgist.com/html/MetalFatigue.htm

http://materials.open.ac.uk/mem/mem_mf.htm

[scrapcan]

Dutchman,

Thanks for pointing out the repetitive stress failure. I was trying to come up with a succinct way to present info from my mechanics of materials training, You did it very nicely.

The thing I came up with as an analogy is the failure of leather shoe laces. over time, even if not over worked, they will fail when used as shoelaces.

[Multigunner]

Heres the point where his formula comes apart, and claiming it to be due to "random error" doesn't feed the bulldog.


The 7x57 Mauser is rated 46,000 CUP, and 51,000 PSI. The
300 Savage is also rated 46,000 CUP, but 47,000 PSI. Random error in both
measurement systems accounts for this discrepancy. Because there is random error in
both measurement systems, any conversion will be approximate, rather than absolutely
precise.

Its not unlike Global Warming advocates, if the data doesn't fit a foregone conclusion ignore it and make excuses.

Pressure readings aren't single round testing, they are averages of many rounds tested, with maximum deviations in each direction.

As the listed data shows the shape of the cartridge case makes a difference in the pressure readings by either system.
Also the point at which a crusher cylinder is in relation to the case makes a difference in the readings, whether the reading is taken at mid body or at case mouth, and same for any other methods.

Differing bullet weight and barrel time are other factors which would alter readings.

PS


Fatigue Failure Analysis
Metal fatigue is a significant problem because it can occur due to repeated loads below the static yield strength. This can result in an unexpected and catastrophic failure in use.





The process of fatigue consists of three stages:

Initial crack initiation
Progressive crack growth across the part
Final sudden fracture of the remaining cross section


http://www.materialsengineer.com/CA-fatigue.htm

[Larry Gibson]

Dutchman

I'll bite;

the part would break after a certain number of load-unload cycles

How many "cycles" would that be and just what "the part" are they talking about? I pondered on that for a while and then read the rest of that report. It’s all about aluminum aircraft alloys used in airplanes.

Ok, I says, Larry let’s give ole dutch the benefit of the doubt here. So I read further into the sources you list. One long report was about firearms (fathom that?) and reading past the catastrophic failure part it says this;

Fatigue - Most firearms of reasonable quality will, with care and maintenance, never fail catastrophically providing none of the foregoing circumstances and deficiencies (a through g, above) are encountered AND ammunition which has been loaded in strict conformity to SAAMI standards for that caliber is used to the exclusion of all others. Factory loads and hand loads intended to increase velocity are normally loaded to the upper limit of acceptable pressures and the continued, long-term use of this ammunition may have a cumulatively weakening effect of the gun assembly which is known as "metal fatigue". Metal fatigue is the result of working loads on the metal producing stresses within the metal which exceed the YIELD strength causing imperceptible changes. Continued and prolonged working loads of this type will produce a cumulative stress which exceeds the ULTIMATE strength of the metal which will then fail.

Now that is what I said with a lot more technological jargon. I also said that age by itself does not cause fatigue or a weakening of the action. I do not believe I stand corrected. You might get me a Cohiba also:smile:

Larry Gibson

[Larry Gibson]

Multigunner

Excellent quotes but are they applicable? That can happen to a new action as well as and old one. What is addressed is Fatigue Failure Analisys meaning that a failure has already occured. The problem stems from the Initial crack initiation . The process of fatigue was started by that. The part broke and continued use after ward resulted in Progressive crack growth across the part and then Final sudden fracture of the remaining cross section .

Age was/is not mentioned as a factor.

Larry Gibson

[frnkeore]

The age factor is what I was refering to when I said "Well said". I have 2 GEW 88's and one 1898 Krag and yes, I've heard about the bolt lug cracks and I know that the heat treatment was done by "eye". I also know of the early barrel failures of the '88's that was corrected. I personally consider the '88 stronger than the Krag.

BUT, I've heard so many people say that you shouldn't load them to there original preasures (not addressing warn parts and head space as the reason) just because they are old guns, more than 110 years old. As far as repeated cycles, both those guns were in service a very short time and by that standard, could be stronger than full auto modern day weapons such as the M16, built mostly of aluminum, that has a fatigue value of about 1/3 steel.

If the stress fatigue were taken seriously, anyone would be a fool to buy a gun of unknown use even if the seller only used factory ammo.

My main focus in rifles are original single shots. I shoot both the weak and strong designs. My oldest gun is a 1876 built cast receiver Ballard, my next oldest is a 1878 Sharps, I also shoot the cast 44 Stevens and they haven't failed in anyway over the 30 years that I've had most of them. I respect the strenght for each type and load accordingly but, I'm not affraid to load 48,000 CUP+ loads in my high walls, 44 1/2 Stevens or even the 1878 Sharps.

I rarely hear about blow up's (most of the accidental ones I've read about in Hatcher's book about the '03), Ackley blew many up testing strenght, I was witness to a cast Ballard blow up from a double charge. But, all in all they are rare! A friend of mine melted the case head out of his well used 700 with a accidental powder over load. It stayed together.

As for CUP and PSI, I see nothing to worry about in modern rifles until well above 52,000 CUP or 62,000 PSI. The primer pocket will tell you that you've gone to far by leaking or the primer falling out. In intermediate strenght rifles like the Win and Marlin levers, they will usually lock up before danger. For the other that are weaker, even, there are plenty of loading manuals to keep you safe but, I guess they could blow up at anytime from low level stress. In that case, we are all on our own.

Mistakes are the real danger in reloading and care needs to be taken assymbling cartridges. Or breech seating as I do mostly.

If we were talking about the design of guns, those things (fatigue and pressure) are important but, we are not, almost all of us use, used guns of some sort.

Frank

[303Guy]

Was it not P. O. Ackly that removed the locking 'lugs' from a 30-30lever action rifle and fired it (remotely) and the bolt remained in place due to the case holding the pressure?

I've seen one Lee Enfield with serious excess headspace eventually sieze due to peening of the locking lug recess. That shows just how much stress excess headspace causes. That same rifle held the case in place with the primer protruding even though the case was lubed and the next case set back onto the bolt face reseating the primer.

Just how much of 'old age' weakness is actually due to increased stress due to wear and the hammer effect? Ever straightened a bent barrel? You can bend it back past the 'straight' point and it simply returns to it's bent position. Straighten it a little beyond 'straight' and give it a quick jerk and it straightens. It's to do with suddenly applied loads. For example, place a load on a scale and it measures some value. Now reduce the measured load by pulling upward with a cord until the scale reads near zero then cut the cord and the scale will momentarily read double the static load. Give that load a clearance above the scale and readings of several times the static load will occur.

One of the Mauser designs was apparently prone to blow-ups with overloads. It was determined that the cause was the rupturing case would seal the locking lug area creating a greatly enlarged surface area for the pressure to act against, causing the blow-up. Something to do with the bolt face design? The Lee Enfield would unlock the bolt head and bend the bolt like a cobra, I am told.

[frnkeore]

Yes, Ackely did remove the bolt on a warn out Win 94 and shoot it successfully but, he reamed the chamber first to improved with little taper and a 40 deg shoulder. He also unscrewed the barrel, 1, 1 1/2 and 2 turns and fired it. Only the oiled cases moved to the rear. Un-oiled the primers just backed out. All his tests with that gun was with factory cartridges no reloads.

Frank

[wiljen]

Someone mentioned that we had the old proof load tests from Hatcher's notebook. I wonder if we ran the tests on those rounds today, how much higher they actually are compared to what they were thought to be in Hatcher's day.

I'm betting that some of those 90,000 CUP loads that were used to proof test were actually well over that #.

[Multigunner]

Yes, Ackely did remove the bolt on a warn out Win 94 and shoot it successfully but, he reamed the chamber first to improved with little taper and a 40 deg shoulder. He also unscrewed the barrel, 1, 1 1/2 and 2 turns and fired it. Only the oiled cases moved to the rear. Un-oiled the primers just backed out. All his tests with that gun was with factory cartridges no reloads.

Frank

It was the locking slides/bolts not the bolt itself.

The primer exerts something in the neighborhood of 900 PSI and if the case walls are gripped tightly enough then the case walls stretch near the head absorbing a good part of the chamber pressure.
The cartridges used were .32 Winchester Special with an Ackley Improved chamber, near cylindrical at case body.

I'm not up on the 94 action but I read that with locking slides removed the bolt can only go back a very short distance before being stopped by the nose of the actuating lever that acts as a safety stop.

[Larry Gibson]

I'm not up on the 94 action but I read that with locking slides removed the bolt can only go back a very short distance before being stopped by the nose of the actuating lever that acts as a safety stop.

Huh?????

Larry Gibson

[frnkeore]

Direct quotes from my 1967 forth printing.

"an old, discarded, beat up Winchester Model 94 rifle was resurrected from the junk pile. The barrel was rechambered for the "improved" 30/30 with a 40 deg shoulder and minimum body taper."

I stand corrected here.

"To farther prove the point, the locking lug was removed from the action entirely leaving the breech block or bolt with no means of support other than the finger lever. The rifle was fired several times with the barrel tight. All cases appeared to be normal except for excessive primer protrusion."

Frank

[Multigunner]

I'm not up on the 94 action but I read that with locking slides removed the bolt can only go back a very short distance before being stopped by the nose of the actuating lever that acts as a safety stop.

Huh?????

Larry Gibson

Just going by something said in a previous discussion, but from the looks of the lever this could be true.

Check the photos here

http://www.castbullet.com/misc/tdown.htm

And parts list here
http://www.urban-armory.com/diagrams/exploded.htm

If the end of the long extension of the lever does prevent the breech block from being blown out by a failure of the locking slides, then its not something you'd want to depend on for repeditive attempts.

Earlier Winchester and Henry rifles up to .44-40 caliber used only the toggle link that actuated the retraction and closing cycles to resist chamber pressure .

PS
I'd read of a similar situation involving a .32 Winchester Special carbine that would "half unbreech itself" on every shot. I may have the two stories conflated.

[frnkeore]

I may be wrong but, it looks to me that if the lever is in the closed position, that the portion on the other side of the lever will be lying nearly parallel to the link and should be below the bolt.

Frank

[Larry Gibson]

Multigunner

I am intimately familiar with the M94 having learned to disassemble and assemble them in '63.

First of all there are not "locking slides" in a M94. You are confusing it with the M92 Winchester which has 2 locking bolts. Those slide up and down the sides of the M92 receiver, in and out of the locking recesses in the sides of the M92's breech bolt. In the M94 there is but one locking bolt and it slides up and down (actuated by the link). The locking bolt locks into recesses in the rear of the receiver and blocks the rear of the breech bolt. The locking bolt can be removed and the breech bolt can then easily be moved back and forth by the lever or by pushing/pulling on the breech bolt.

Were the rifle fired without the locking bolt the rearward thrust of the breech bolt would easily push the "end of the long extention" back with it and would continue rear ward. No, it is not "something you'd want to depend". Best to keep the locking bolt in place, that's what it's there for.

Back in my youger, dumber days I loaded 30-30s to point in a M94 until the breech bolt began pushing the locking bolt down basically unlocking it. Not hard to do with a M94 in 30-30 or 32WCF, just dumb to do is all. After all...your face is just a few inches behind the breech bolt.

Larry Gibson

[Multigunner]

First of all there are not "locking slides" in a M94. You are confusing it with the M92 Winchester which has 2 locking bolts. Those slide up and down the sides of the M92 receiver, in and out of the locking recesses in the sides of the M92's breech bolt.
I had thought the 94 locked in the same manner.

Looking closer at the schematics it looks like what had been seperate Slides are joined into a single unit with the connecting center section locking into the underside of the breech bolt.
Probably not stronger so much as less subject to friction.

[Larry Gibson]

Perhaps more "hands on" with a real rifle and a little less "internet" schematic viewing theory would give you a better idea of what the parts really are(?).

Larry Gibson

[Multigunner]

Perhaps more "hands on" with a real rifle and a little less "internet" schematic viewing theory would give you a better idea of what the parts really are(?).

Larry Gibson


What part of


I'm not up on the 94 action but I read that
Do you not understand?

I have very little interest in lever actions, so I don't pretend to be an expert on the subject.

and as Frank quoted from the article


"To farther prove the point, the locking lug was removed from the action entirely leaving the breech block or bolt with no means of support other than the finger lever.
Which indicates that the "finger lever" does in some way provide a minimum of support.
Its not as if I recommended that anyone try this at home.

If everyone here had a speciman of every type of rifle at hand to check the fit of parts there would be no need for discussions like these now would there.


PS
I've been looking for sources that discuss age embrittlement of steel objects a century or so old.
This is as close as I've found so far.



When steel is cold bent or cold worked, a process called "Strain‑Age Embrittlement" commences immediately. The steel's crystal structure begins to reorganize, and with time, the cold worked area becomes increasingly brittle and the fracture toughness is decreased.
Normally this process would not be a problem, so long as adequate alloying agents are used.
The hammering that locking lugs and recesses take, as 303 guy mentioned, are a form of cold working of heat treated steels. In some cases, like the SMLE, the metal of the recesses is heat treated seperately from the rest of the action body or bolt body.
The quality of the steel makes a great difference.

Nitrogen compound infiltration of micro fractures of ferrous metals can also lead to crack propagation while the object is at rest and not under stress.



Term: Strain-Age Embrittlement

Description: A loss in ductility accompanied by an increase in hardness and strength that occurs when lowcarbon steel (especially rimmed or capped steel) is aged following plastic deformation. The degree of embrittlement is a function of aging time and temperature, occurring in a matter of minutes at about 200 °C (400 °F) but requiring a few hours to a year at room temperature.





This phenomenon applies to carbon and low alloy steel. It involves ferrite forming a compound with nitrogen; iron-nitride (Fe4N). Temperatures around 250°C, will cause a fine precipitation of this compound to occur. It will tend to pin any dislocations in the structure that have been created by cold work or plastic deformation.
Strain ageing increases tensile strength but significantly reduces ductility and toughness.

[wiljen]

Alright this was my thread and I'm not gonna watch it turn into a pissing contest over who's right as it drifts off topic. Both of you quit the bickering.

[Larry Gibson]

Multigunner

Perhaps I was a bit to abrupt but my comment was not intended as criticism or as "bickering" as wiljen took it. My opologies to both as that was not my intent. My intent was simply it is more fun and and we get a better insight with "hands on" experience with firearms vs scematic drawings, most of us anyways. It was just obvious from your posts that you had little or no actual experience with either rifle discussed. Nothing wrong there either as asking questions and discussing things here is how many learn. My attempt to denote the differences between the two actions was not an attempt to "bicker" Or be "right" but simply to inform and educate you on the differences between the 2 actions and the correct names of the parts. Obviously I failed to get that across. Again my apologies.

Drop by a gunshop or two and look the 2 different rifles over and you see the differences mentioned. That should be a lot more fun than deciphering schematic drawings, it is for me anyways.

Larry Gibson

[Multigunner]

Larry

So do you doubt the account of Ackley's experiment?
I have my reservations.


PS
As I've said on several occasions, I have little interest in lever action rifles, mainly because an old and poorly healed injury to my right hand makes operating a lever action awkward and painful.

[fatnhappy]

Alright this was my thread and I'm not gonna watch it turn into a pissing contest over who's right as it drifts off topic. Both of you quit the bickering.

I thought you guys were on sabatical?

:kidding:

[wiljen]

I thought you guys were on sabatical?

:kidding:

Spoken as the OP, not a mod. :)

[Larry Gibson]

Larry

So do you doubt the account of Ackley's experiment?
I have my reservations.


PS
As I've said on several occasions, I have little interest in lever action rifles, mainly because an old and poorly healed injury to my right hand makes operating a lever action awkward and painful.

No, I don't doubt it at all. Even using the standard 30-30 case in a clean dry chamber it takes 40,000+ psi for the rear thrust to overcome the grip the case has on the chamber walls and drive the case back against the breech bolt. Most M94s don't have very tight headspace for the rim. This is why with normal loads we see backed out primers all the time. Ackley used an improved chamber with minimal case taper and 40 degree shoulders. This allowed the firing of factory 30-30 cases without the breech block in the rifle with the cases expanding and gripping ths chamber walls with little thrust on the breech bolt at all.

Remember also the amount of pressure to expand a case in a normal chamber. There is an "offset" of 7,000 psi used to account for this. Add in the additional pressure needed to fire form the case in the improved chamber and quite a bit of a regular 30-30's psi was used up there. Fire a test string in FL sized cases, then fire the same identical load in fully fire formed NS'd cases. Odds are the velocity will be higher with the string using fire formed cases. The reason is it takes energy to expand the case. That energy comes from the available power provided by the powder charge. Energy used to expand the cases detracts from that available to push on the bullet and the FL sized cases should have less velocitiy.

Larry Gibson

[Multigunner]

Heres a rather detailed article on effects of chamber finish on case wall grip and stretching of case bodies.
http://www.varmintal.net/a243zold.htm

One thing to remember is that milspec ammunition with crimped primers won't allow the primer to back out and cushion impact of the head of an oily or wet cartridge case.

There have been automatic cannon that used a system where the cartridge was propelled into the chamber (perhaps by a small charge) from a cuplike carrier on the ammo belt. The cannon rounds ignited while still moving forwards. The empty case was blown back into the carrier.
I suspect the grip of the casing on the chamber wall was a factor there, slowing the blowback of the casings.


PS
Since we know that blow back and delayed blowback weapons chambered for high power cartridges such as the 8mm Mauser do work, its obvious that the results obtained by P O Akley can only be judged as a special case involving a particular chamber geometry and pressure range.

The duration of the momentary grip of the case by chamber walls depends on bullet/barrel time and how far and how fast pressure drops.

IIRC
Maximum pressure generally occurs within the first 10 or twelve inches of bullet travel, pressure then begins to slack off. The bullet is at that point already moving at a fairly high velocity and though pressure is dropping rapidly the gases still accelerate the bullet till it leaves the muzzle.
At some point pressure would drop enough for the grip of the case walls to be negated while some residual pressure remains to push the case back against the breech face.

I just found a study of the effects of lubrication of cartridges in a blow back system. Its found in George Chinn's 4th volume of his work on the Machine Gun.
While this study was concerned with utilizing this effect to drive the system, it does explain very nicely just why lubricated cases can be very damaging to a bolt action.
Not only is friction negated, lubricant trapped between case shoulder and chamber is subjected to intense pressure. The lubricant is relatively incompressable so the case then acts like a hydraulic ram slamming the case head into the bolt face with far more energy than would normally be brought to bear.

[303Guy]

Two points come to mind; firstly, if Ackley's chamber had been modified, it is also likely to have been somewhat rough as in not polished. Second, according to Varmint Al's simulations, the primer exerts quite a force on the bolt face so even if the case could support itself, something must have been holding the bolt in place. Mind you, a factory loading in an enlarged chamber should produce faily moderate pressure over and above the energy absorbed in expanding the case.

My assertions are that a lightly lubed case will still grip the chamber walls but not enough to cause the thrust to be carried by the web area, meaning the case will progressively creap rearward with the shoulder area remaining in position so that no part of the case gets stressed beyond it's elastic limit. The converse is where the case wall grips the chamber and the web fails. Most often, I would suggest the case walls grip firmly then suddenly release at high pressure allowing the case head to contact the bolt face with sudden force. Notice how in the simulation, the lubed case bolt face thrust rises at a lower rate begining earlier and the plastic deformation is lowest although bolt face thrust is higher.

[Multigunner]

Two points come to mind; firstly, if Ackley's chamber had been modified, it is also likely to have been somewhat rough as in not polished. Second, according to Varmint Al's simulations, the primer exerts quite a force on the bolt face so even if the case could support itself, something must have been holding the bolt in place. Mind you, a factory loading in an enlarged chamber should produce faily moderate pressure over and above the energy absorbed in expanding the case.
Sounds right to me.



My assertions are that a lightly lubed case will still grip the chamber walls but not enough to cause the thrust to be carried by the web area, meaning the case will progressively creap rearward with the shoulder area remaining in position so that no part of the case gets stressed beyond it's elastic limit. The converse is where the case wall grips the chamber and the web fails. Most often, I would suggest the case walls grip firmly then suddenly release at high pressure allowing the case head to contact the bolt face with sudden force. Notice how in the simulation, the lubed case bolt face thrust rises at a lower rate begining earlier and the plastic deformation is lowest although bolt face thrust is higher.

George Chinn went into some detail on the differing effects of heavy lube vs Light oils.
In the case of the blowback weapons he was describing they were looking to increase thrust on the bolt face and avoid any case stretching and separation. These being chambered for cartridges much more powerful than the pistol size cartridges most blowback weapons are chambered for.

According to Chinn the surface of a nice shiny cartridge case looks slick as glass, but under a microscope its revealed to be covered with tiny pits and fissures.
When a thin layer of a light oil is applied to a case and the cartridge fired, the oil is pushed into the surface imperfections leaving the high spots to make metal to metal contact as if with no lubrication at all. The exact same portion of the surface made the exact same level of contact with the chamber walls.

When I load up rounds that I intend to store for future use I polish the cases bright, then rub them down with a cloth moistened with WD-40 or a similar generic oil. These have preservative laquers in solution, so when dry they leave a microscopic layer of protection, but not a layer that could act as a lubricant under such high pressures.
The British did the same when they "oiled in the service manner" ammunition that would be exposed to dirt and sand. The micro thin protective layer discouraged dust or mud from clinging to the surfaces. At the same time they warned against leaving a noticable amount of oil in chamber or bore.

[Larry Gibson]

Instead of second guessing what Ackley did you might read his books. What you're guessing at is on page 138 of vol I, Handbook for Shooters & Reloaders. There are also pictures of the cases used in the test. I might add also if you've ever seen any of Ackleys work or know of him you'd understand the obsurdity of "if Ackley's chamber had been modified, it is also likely to have been somewhat rough as in not polished". Were Ackley to have read that I'd bet you get a few "terse" words in reply from him.

Also remember this was "back in the day" when all chambers were "polished". Actually it was called "burnished" and a special burnishing reamer was made to use after the finish reamer. It's too bad burnishing reamers are still not in use these days. Especially in S&Ws, Colts and Rugers whose chambers used to be smooth as a babies butt. Now they all look like they were chambered with a chinese drill bit.

Larry Gibson

[303Guy]

Fair 'nuff. I made that comment after looking at my reamed No4 barrel chamber. It's not rough but neither is it polished mirror smooth. Without lube, it will separate the case head in three or four firings. Being on the engineering side of things and having a basic understanding of the roughness of 'polished' surfaces, I felt Ackley would understand where I was coming from - but I could be wrong (on both counts!)

The thing is, we humans cannot imagine the forces and sheer speed involved in the firing of a cartridge. It's a bit like trying to understand the value of infinity or even zero for that matter. (Try understanding infinity divided by zero! :shock: )

Something I have noticed is that even a 'well lubricated' case will come out feeling dry. By well lubricated I mean enough lube to actually size a case with. (I do that for fire-forming new cases with lighter loads).

[Multigunner]

Fair 'nuff. I made that comment after looking at my reamed No4 barrel chamber. It's not rough but neither is it polished mirror smooth. Without lube, it will separate the case head in three or four firings. Being on the engineering side of things and having a basic understanding of the roughness of 'polished' surfaces, I felt Ackley would understand where I was coming from - but I could be wrong (on both counts!)

The thing is, we humans cannot imagine the forces and sheer speed involved in the firing of a cartridge. It's a bit like trying to understand the value of infinity or even zero for that matter. (Try understanding infinity divided by zero! :shock: )

Something I have noticed is that even a 'well lubricated' case will come out feeling dry. By well lubricated I mean enough lube to actually size a case with. (I do that for fire-forming new cases with lighter loads).

As Chinn and others discovered, what looks to be slick as a ribbon is not so slick when viewed at high magnification.

Larry mentioned the burnishing reamer. Burnishing will smooth a surface far more than can be done by any polishing compound. How smooth would be a question best answered by a powerful microscope.

Even the honed and stropped edge of a razor looks like a mountain range under high magnification.

I'll try to type up a copy of relevant comments I found in Chinn's book and add them to a post here.
Not all such information will appear to apply unless all is weeded through and a full picture emerges.

PS
It is hard to concieve of the speed with which things happen between pulling the trigger and the bullet leaving the muzzle, but if you think of things as following a natural course of action and reaction in finite moments of time it becomes more clear. Every chemical action requires a finite period of time, no matter how short that period is nothing is instantaneous.

[303Guy]

... no matter how short that period is nothing is instantaneous. Quite so but there are additional factores we don't think of at high speeds like differences in pressure between the base volume of the case and the neck volume, all due to pressure waves and the 'insulating' effect of the mass of powder in between and so on. It's quite complex compared to our observable world of slow motion. I have a case with a dent in it starting at the shoulder junction that is quite baffling to me. It happened during firing and is not the first but it only happens with this one rifle, a 303-25

http://i388.photobucket.com/albums/oo327/303Guy/MVC-553F.jpg