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Discussion Starter #1
With modern pressure testing equipment being used more widely by the ammunition industry (even as I type), we observe published load data becoming a bit more conservative. Recalls on data (for hand loaders) and store bought ammunition has become fairly common.
I’m talking copper-crusher vs. transducer systems here. Has anyone seen data or measured any pre-transducer factory ammunition with a transducer system?
As a side question, I wonder what some of the old “Blue-pill” loads would show?

Cheezywan
 

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As the pressure testing equipment becomes more accurate we are find many of the old load recomendations wer higher pressure than we thought at the time
 

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Don't see this as a bad thing, makes sense to me. More accurate data replacing less accurate data.

I think of it this way... I get a new phone book every year; it's a lot less frustrating to dial the number from this year's book than from one published in 1955.
 

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The Hog Whisperer (Administrator)
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I think John is right. Everyone says that the loads have been watered down by lawyers (and some cartridges have had their pressure ceilings officially reduced by SAAMI), but if you have a program like Quickload you'll find that the majority of the data is pretty reasonable. Either that, or a global conspiracy to reduce published data ;)

Rather than complain about the reduced data, recognize that we are in the golden age of handloading. There are more powders and bullet choices than ever before, and measuring equipment like chronographs and even pressure trace is very affordable to the average user.

It might be kind of scary to run some of the old loads across modern equipment! Kinda makes you appreciate the safety margin that is built in to most guns.....
 
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I think John is right. Everyone says that the loads have been watered down by lawyers (and some cartridges have had their pressure ceilings officially reduced by SAAMI), but if you have a program like Quickload you'll find that the majority of the data is pretty reasonable. Either that, or a global conspiracy to reduce published data ;)

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Exactly, the 7mm REM mag and the 243 win are 2 such examples, that exhibit sudden high pressure spikes. The 6mm Rem dose not exhibit such behavior, nor does other 7mm chamberings. If in a test string if the measured pressure rises above the absolute max allowed or the average is above the max allowed average, then the data is backed down so this does not occur. Why are some cartridges prone to this behavior while other are not? That my friend is the 60 million dollar question
 

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Discussion Starter #6
I did not mean to sound as though I was criticizing the ammunition makers.

More interested to know what the pressures were before the use of strain gage equipment became as common as it is. I did not intend this thread as a “rant” in any way.

My interest is in the actual numbers.

I have some boxes of factory ammunition on the shelf from the eighties. I figure a bunch of you folk’s likely do too.
Has anyone on this board seen some of the older ammo tested?

I like the new loads and data. I use it too (with discretion)!

New telephone book may be more accurate, but it sure is tougher to read!


Cheezywan
 

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Anyone remember the Supervel ammo? very hot loaded handgun fodder. Imagine the new measuring devices would give the manufacture and manual publishers heart problems if still made.

I've never had a problem trying to follow the published loadings - years ago or today. Very rarely, a certain rifle/cartridge will like a load just a grain or two above the recommended, but as a rule, loading just a bit below maximum published provides the best accuracy and gives satisfactory velocity.
 

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I'm loading my 44Mag Contender with "old" data that probably creates more pressure than the modern SAAMI spec. and with the pressure signs (slightly flattened primers) I would never consider using the same loads in a revolver. Like Mike said, it's reassuring to know there are a lot of quality guns our there with a safety margin.

I would never suggest to someone that they exceed published data, particularly if the same source has revised and lowered their maximum charge weight, but part of me does wonder: If people have shot millions of a certain recipe handload through their SBH's or '94 carbines, with no case failures and no evidence of frames stretching or actions loosening up...where is the problem with the data? Is there a point where empirical data trumps science, or do we show blind faith to the almighty transducer and drop our charges by a grain, across the board? (Is anyone aware of instances where maximum charges have been increased as a result of better pressure testing technology? If not, isn't that suspicious?)

I'm sure this pot has been stirred a'plenty, and I'm not one of those old-timers who ignores change and progress, but if your particular load allows you to get 10-12 firings before the brass starts to fail, and your gun never complains, how can that recipe all of a sudden be dangerous? Paradoxically, manufacturing processes and metallurgy have made advancements for both case and chamber, but now a new means of measuring pressure insists the old loads aren't safe?

I will ALWAYS refer to the load books, rarely, if ever, exceed them and continue to use best practices when reloading ammunition. However, I will also exercise my own good judgment when deciding whether or not to discount old recipes, just because some egg-head tells me they've been wrong all along.
 

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There are three limitations with the old copper crushers. One is non-linear response. The crusher can track pressure ratios pretty well up to around 30,000 psi. As you go above that, each additional psi produces progressively less response in the crusher pellet. I have one graph showing the .30-06, in being loaded from 12,000 to 24.000 psi (real), gets crusher readings that likewise double. But in going from 24,000 psi to 48,000 psi real pressure, the crusher reading only indicate about 2/3 increase. Going from 48,000 psi to 96,000 psi, the crusher reads only about 1/2 again higher for the second number.

As a result, it isn't just the absolute peak pressure readings that were wrong, but the amounts of intentional increases were much higher than previously thought. The old Blue Pills that were supposed to be in the 70-75 kpsi range, were probably closer to 95,000 psi.

A second problem is inertial integration. That is, the mass of the crusher piston tends to smooth the bumps out of the pressure curve because it can't respond to them fast enough. In the end, it gives just one reading representing an averaged pressure peak, but it doesn't tell you what that peak was comprised of. Piezo transducers initially copied the basic crusher format with a piston and all that, and a lot of instruments were just to read the peak again (rather than the more complicated process of photographing an oscilloscope trace). The peaks are higher because they are linear, but the piston still smooths over very short spikes.

The later conformal Piezo transducers and strain gauge instruments both respond much faster, and computers now will digitally record their response and produce a trace file that can be saved for examination. With the newer instrumentation, short and anomalous pressure spikes become apparent in some loads. That did indeed result in backing some loads off because the phenomenon isn't understood, is often erratic, meaning it likely happens in some chambers and not others. Look at Rocky Raab's post #21 in this thread on Alliant's Blue Dot warning for an example.

A third problem with the crushers is repeatability. Precision Shooting had an article on this sometime in the late 90's. It turns out that reference ammo sent for crusher testing at a number of different labs got a number of different results. Everything from the individual test instrument's chamber dimensions to how delicate a feel the test technician has with his micrometer (and whether he checks its calibration) can move the readings around significantly. I believe I recall them concluding that crushers were just too irregular to be trusted as a pressure standard.

With all that in mind, you can understand how some commercial loads tested by crusher got to market clearly too warm in most guns. Of course, that experimental error is just one of the variables in manufacturing that can cause a recall. One thing a crusher does work for, assuming you use the same one and the same technician on a day when the temperature is the same, is duplicating charges using different lots of the same powder. That adjustment can be made with one.

A lot of shooters take little interest in the above, figuring its all relative. But to engineers planning gun design life based on how much stress the steel is subjected to, those crusher errors can easily erase their design safety margins.

Shooters most often depend on reading their brass for pressure indication (see the pressure sign sticky). Brass readings are, themselves, analogous to crusher readings, as when the head acts like the crusher pellet and you read its expansion or the primer pocket's expansion. An important difference is the brass head isn't calibrated. The copper crusher slugs come with a triage table showing exactly how much they deformed under some degree of static pressure applied by standard weights. Cutting open a few different makes of cartridge cases will quickly tell your eye that the differences in brass shape and head configuration cannot possibly all expand the same amount at the same pressure. And they don't.

In addition to the dimensional differences, case head and other brass hardness depends on both the alloy specifics and on how much the forming dies work harden it. Hatcher describes how he needed some extra hard caseheads for high pressure destructive tests, and got it just by having the headstamps struck deeper. I wouldn't be surprised, therefore, if the number of characters in a headstamp affected head hardness, too. As a result of all the variables, some brass gives out long before the steel gets near its elastic limits, but other brass doesn't. The difference usually is not catastrophic, but rather results in cumulative damage. Gradual bolt setback is one observed example. A lower load pressure spike may cause chamber ringing, another problem not indicated by brass pressure signs.

Sometimes brass provides an elastic limit test, as when a bolt gets sticky to open, or when a revolver's ejection gets sticky. The is the result of the steel straining enough to allow the brass to expand beyond its yield point, so the steel snaps back over it like a kind of unlubricated sizing die. This is another area where brass grain size and work hardening will vary the actual pressure at which it happens, and therefore the actual amount it is indicating the steel is being stretched. Shooting a lot of rounds that cause sticking is a great way to introduce gun steel fatigue.

To Cheezy's question, I don't know of anyone retro-checking old commercial loads. If I had a large lot of surplus ammo to sell, I'd sure pay a lab to do it, but with a few rounds here and there in people's gun cabinets, I don't see any economic incentive for commercial testing of old lots. It's pretty much going to be the private users of the Pressure Trace instrument or other strain gauge gear who might check? They can compared it to current run ammo that is sold as the nearest equivalent to the old, but when you consider that bullet pull tends to increase over time, you still won't really know the peak pressure it was loaded to originally? I do know the U.S. Navy tested some artificially aged (by heat) 7.62 loads in the 70's that had their pressure increase about 50%. This was due to deterrent coatings deteriorating, leaving the powder with a faster burn rate than it had originally.
 

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Thanks, Unclenick -

Very authorative and informational. Hope members take the time to read this post and take it to heart.
 
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Unclenick,

I don't understand this sentence in your last post.

"A lower load pressure spike issue that doesn't show up in the brass in advance is chamber ringing is another problem not indicated by brass pressure signs."

Other than that sentence you helped greatly in my understanding. Make me wonder if I should be shooting those 30-06 180 gr. silvertips that my dad bought in the 1960's? :eek:
 

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Discussion Starter #12
Unclenick, you sure know how to get your head wrapped around this stuff! Thank you for the thought that you put into your post (and taking the time to type it).

I have no pressure testing gear or computer programs to work with. “Bullet clock” and my hand loading tools is it.

If I did have the equipment to measure pressure, I might be inclined to sorta reverse engineer them.

Two that come to mind are 45-70 Government and 30 WCF. Both started with black powder loads.

Something like this?

#1 Duplicate the original load of black and measure the pressure.
#2 Measure the pressure of current factory loaded ammunition.
#3 Measure the pressure of some “vintage” factory ammunition.
#4 Measure the pressure of some hand loads with “vintage” components and data.
#5 Measure the pressure of some hand loads with “current” components and data
#6 Compare all to current SAAMI specifications, and to each other.

I’m not a lab technician, so I very likely overlooked something simple. Also, access to “vintage” stuff is kinda restricted to “what you have available to you”.
Add your thoughts if you care to.


Cheezywan
 

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I'll save Nick some typing in the future, and make this a sticky. :)
 

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My understanding on reduced loads compared to older data was because many older guns are still in use and gun metal does suffer fatigue over many years of use. Lawyers certainly do have a say in the matter. Lawsuits today can be in millions of $$. Courts no longer require people to use common sense or hold them accountable for their own stupidity. Modern guns are usually built much stronger than guns made before or during WW11 but many pre-war guns are still being used and some have lost some of their original strength over time. Some older actions such as early lever guns were weak by design compared to modern Lever guns using the same cartridge. Factory 8MM Mauser is loaded far below it's potential in north America but is often still loaded to max pressures in Europe. That is all about lawyers in the US.
I wouldn't reduce a load that I have been using for many years in the same gun without problems because of a new loading manual, but if I were to start loading for a different caliber and gun I would use the new load manuals. I don't load HOT for caliber. I load for accuracy and consistency for a particular gun. If I want more velocity or power than the loading manual allows for that caliber, I will use a bigger gun rather than push unsafe limits trying to squeeze an extra few FPS out of a smaller caliber. An extra 150 FPS in any caliber will make no difference at all in determining whether you bring home the venison or any other game.
 

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This thread is over two years old. I note that I never saw Scruffy's question, but went back and reworded what was apparently a cut-and-paste hybrid of two attempts at the same sentence that were never reconciled.

If a gun shoots accurately, that's a very good sign the metal isn't being mistreated, regardless of how the loads compare to the manuals. Fear of pressure excesses in old guns is greater in the U.S. not only for liability reasons, but because the CIP in Europe, unlike SAAMI here, has actual legal authority and uses it to force surplus guns to be reproofed before they can be distributed for sale. That does give them a higher margin of certainty that the gun is up to modern ammunition. It also means guns cost more and have to be licensed so they can track that kind of thing.

Below is an example from SAAMI documentation illustrating just how far off copper crushers can be.

Code:
[B]From Page 119 of the SAAMI Centerfire Rifle Document                
LOT NO: 30 CARB-110-4WW Reference Pressure Loads [/B]               
Facility           MV       Vel. SD    Peak Pressure   Pressure SD
Blount          2036 fps    15.0 fps     37200 CUP      1180 CUP
Federal         1983 fps    21.0 fps     33400 CUP       940 CUP
Hercules        2015 fps     5.0 fps     41200 CUP      1720 CUP
Hornady         2044 fps    11.0 fps     36500 CUP      1350 CUP
Olin Mfg.       2004 fps    14.0 fps     32800 CUP      1000 CUP
Olin R&D        2020 fps    12.5 fps     37800 CUP      1170 CUP
Olin St.Marks   2014 fps    22.0 fps     37100 CUP      1100 CUP
Rem., Ilion     2046 fps    10.0 fps     37000 CUP      2800 CUP
Rem., Lonoke    1975 fps     8.6 fps     33700 CUP      1790 CUP
                
[B]Extreme Spread [/B]    3.52%                    23.14%    
[B]Average [/B]        2015 fps      13 fps     36300 CUP      1450 CUP
 

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Discussion Starter #16
Thanks for contributing again unclenick. Good stuff!

I have intentions to clock some 1980's vintage ammunition sometime soon. Remember it shot fine in the day.

No pressure testing stuff here. Just a bullet clock.

I hate to say it, but. I have lived long enough to accumulate antique ammunition.

Everyone stay safe and thanks for posting.

Cheezywan
 

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After reading the posts to date on this Thread, I still am left with some questions.
in an original Winchester 1873 serial number 5961_ and chambered in what is now called 44-40 or .44WCF the original loadings were in Balloon base cases filled with black powder pushing Lead bullets of around 200-220 grains and .433-.434 diameter out 22 to 24 inch barrels.

Supposedly these are 'weak' action design firearms.

Modern ammunition is loaded in solid base cases using 'reduced' loadings and .429-.430 diameter either lead or Jacketed bullets to unknown PSI as SAMMI seems to still list it at 13000CUP.

I know that the original loads held more BP than modern case capacity.
I know the rifles were accurate at the time and used to ranges in the 800 to 1000 yard extremes at times, but normally around 100 to 400 yards.

Modern factory loadings are NOT accurate out of this particular gun nor any I have been privileged to fire. some examples are at 100yards totally missing a 24 inch wide by 48 inch tall target frame holding a 12 inch diameter bull two shots out of five from a sandbag bench rest shooting position, of the three that hit the paper, one was in the black and two were on cardboard. Also there were indications of load problems on the extracted cases, with powder burn residue on the outside of the cases and occasional splits lengthwise in shoulder and neck.

Hand loads work MUCH better, but with BP only weighing about 20 grains filling the modern case to the base of the bullet, I believe these are still 'reduced' loads. They do all reach the target,usually five out of five in the black, clustered around a 3 inch circle.

What are the velocities and pressures, I do not know because I do not have the measuring tools needed to find out.

I also have Smokeless powder loads in 200 to 220 grain Lead that are accurate, but I am not stating the powder nor charge so as not to run afoul of forum rules.

The Question is WILL anyone run pressure instrument tests on these old calibers to see what they really produced and what they are now producing?

Am I wrong to believe the 'aging steels' argument was addressed in the change from Balloon base to solid base cases?

Admittedly, most modern users of the 1873 Winchester are in 'Cowboy' competitions, not in 'long range' target shooting nor in hunting situations; but it still should be addressed sometime and somewhere.

Another Example: The Stevens Favorite Take-down rifles of the 1894 model are mostly chambered in .22RF, .25RF., and .32RF calibers from the original BP era and transitioned to Smokeless Powder loading up until all production was halted in 1942 for the WW2 production needs.
Now days people state that these are old and weak and are not suitable for modern cartridges such as the .22WMR or conversion to such as the .25ACP cartridges.
I believe any action that can stand up to a .32 Long RF loading in BP would stand up to .25ACP or .22WMR modern loadings. Do the math with the Pmax data and base areas.
The .32 Long RF loaded 18grains of BP behind a 90 grain lead bullet at 1080fps.
The .25 Stevens RF was loaded to a Pmax of 23000PSI as late as 1971 (68Gr Lead at 1180fps).
The .22WMR is loaded to Pmax of 24000PSI and uses a 40 grain bullet at 1480fps.
The .25ACP is loaded to Pmax of 25000PSI and uses 35 to 50 Grain bullets at from 700fps to 1000fps.

Best Regards,
Chev. William
 

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…in an original Winchester 1873 serial number 5961_ and chambered in what is now called 44-40 or .44WCF the original loadings were in Balloon base cases filled with black powder pushing Lead bullets of around 200-220 grains and .433-.434 diameter out 22 to 24 inch barrels.
I thought the first of those rifles had 30" barrels and the shorter ones were carbines? But I'm not positive.

Supposedly these are 'weak' action design firearms.
Compared to a modern guns, yes they are weaker. Even a modern copy of the 1873 would have better controlled metallurgy.

Modern ammunition is loaded in solid base cases using 'reduced' loadings and .429-.430 diameter either lead or Jacketed bullets to unknown PSI as SAMMI seems to still list it at 13000CUP.
It won't be unknown to the manufacturer. He'll likely follow the SAAMI standard, which puts a maximum on pressure and has a recommended velocity range for each round. Keep in mind that SAAMI is a manufacturer's association, so they devise their load pressures for worst case guns they anticipate them being fired in.

I know that the original loads held more BP than modern case capacity.
And they were probably compressed loads, too. The old .45-70 loads were. That said, the velocities reached with 40 grains of black powder in that cartridge can be reached in current brass with less than 10 grains of many modern smokeless powders. The chemistry of black powder has lower total stored energy per grain than smokeless does. With a full balloon head case, though, I don't know what the original case capacity was.

Modern factory loadings are NOT accurate out of this particular gun …Also there were indications of load problems on the extracted cases, with powder burn residue on the outside of the cases and occasional splits lengthwise in shoulder and neck.
That outside neck staining is an indication of the pressure being low for the powder chosen. Sounds like they should have selected a different powder. Trail Boss will burn very cleanly at these lower temperatures and pressures and probably makes a good choice.

Hand loads work MUCH better, but with BP only weighing about 20 grains filling the modern case to the base of the bullet, I believe these are still 'reduced' loads.
Since I don't know the capacity of the original balloon head cases, I can't really guess at how compressed the charge was. You might check at the Castboolitz forum to see if anyone there has some ideas about that. I would think, even with a modern case, you should still be able to squeeze 30 grains in. You will probably need a long drop tube and a lot of compression.

What are the velocities and pressures, I do not know because I do not nhave the treasuring tools needed to find out.
They can be purchased: RSI - PressureTrace

I also have Smokeless powder loads in 200 to 220 grain Lead that are accurate, but I am not stating the powder nor charge so as not to run afoul of forum rules.
If your loads are over published load levels, this isn't a problem if you copy over the warning in bold, here, then paste it into your post. Can't really have a reloading forum without mention of loads.

The Question is WILL anyone run pressure instrument tests on these old calibers to see what they really produced and what they are now producing?
Sounds like you've found yourself a project! I'm sure no modern facility will let black powder anywhere near their expensive pressure test guns, but if you have a gun you use it in anyway, and you get the Pressure Trace instrument, you can do it for yourself.

Am I wrong to believe the 'aging steels' argument was addressed in the change from Balloon base to solid base cases?
Yes, you're wrong. The issue isn't "aging" of the steel, per se, unless corrosion has occurred. Rather, it's about how long ago they could do reliable temperature control for casting and heat treating and controlling forging temperatures. The problem is that they used to judge temperature by eyeballing the color of the heated steel. It wasn't until the blow-up problems with some early Springfield '03 receivers were investigated in the 1920's that it was concluded that even the most skilled worker could be off several hundred degrees if the lighting on the shop floor changed. This was in the days when factories depended on skylights, so it changed frequently.

The result of overheating is so-called "burned steel", which means the excess temperature caused excess grain growth. The yield point in steel is more dependent on its grain size than on its hardness, so this meant the "burned steel" was weak. They replaced "eyeballing" with pyrometers to address the problem in the 1920's, but earlier guns didn't have that advantage. So it's really about irregularity steel production in the 19th century.

As to the thicker brass, that addresses head blow-outs, specifically. It won't matter much otherwise in the .44-40 because the pressure is too low to stick the brass to the chamber wall so it won't absorb force by stretching, as high power rifles do, and instead will simply back up like a little piston, uninhibited in terms of the amount of rearward force it applies.

But, that said, I think the 13,000 CUP limit on the .44-40 probably has mainly to do with shooting it in old revolvers where the web of steel in the chambers at the perimeter of the cylinder can be very thin. Assuming the 1873 isn't that thin anywhere (I don't have one to look at, but wouldn't expect it to be), I'd be very surprised if even an old one couldn't tolerate the same pressures a trapdoor Springfield does, and those are generally held to about 20,000 CUP.

Admittedly, most modern users of the 1873 Winchester are in 'Cowboy' competitions, not in 'long range' target shooting nor in hunting situations; but it still should be addressed sometime and somewhere.
Still sounds like you've found a good project.

Another Example: The Stevens Favorite Take-down rifles of the 1894 model are mostly chambered in .22RF, .25RF., and .32RF calibers from the original BP era and transitioned to Smokeless Powder loading up until all production was halted in 1942 for the WW2 production needs.
Now days people state that these are old and weak and are not suitable for modern cartridges such as the .22WMR or conversion to such as the .25ACP cartridges.
I believe any action that can stand up to a .32 Long RF loading in BP would stand up to .25ACP or .22WMR modern loadings. Do the math with the Pmax data and base areas.
The .32 Long RF loaded 18grains of BP behind a 90 grain lead bullet at 1080fps.
The .25 Stevens RF was loaded to a Pmax of 23000PSI as late as 1971 (68Gr Lead at 1180fps).
The .22WMR is loaded to Pmax of 24000PSI and uses a 40 grain bullet at 1480fps.
The .25ACP is loaded to Pmax of 25000PSI and uses 35 to 50 Grain bullets at from 700fps to 1000fps.
Yes, the weak steel argument in those cases seems a little lame. However, there can be design issues, too. I have an old Winchester pump in .22 WRF that blows case rims open with modern loads. It wasn't designed with any support around the head, which just sits proud of a flat surface at the breech of the gun. If I were to rechamber it for .22 Magnum, I think every shot would blow out at the head.

Let us know if you learn more?
 

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Thank you for your kind explanations and comments on my post.
From what I see on the PTI web site the system cost between $500 and $800 for a system that will require additional expenditures for Portable Computer (Laptop?).
At this time in my life Iam on limited income (Social Security and a Military disability retirement) and the necessary funds to purchase the instrumentation is not available.

I guess that someone else will need to become sufficiently interested to take up the investigation.

I did note that the strain gauge MIGHT fit in the clearance (about .010 diameter difference between the Stevens Favorite take-down receiver barrel socket and the barrel spigot, but I did not see information as to the stain gauge mounted thickness, the extension wire sizes nor the connector dimensions to determine to any certainty if connections could be made.

Best Regards,
Chev. William
(ETC USN Retired, Agent Orange and Ionizing Radiation listed Veteran)
 

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Take a look at the RSI video for installing a strain gauge to get some idea by seeing the size of the hand installing them.

The type of gauge itself is a foil strain gauge. They've been around for decades (RSI doesn't make them; they buy them from Micro-Measurements or HBM or other established maker). They consist of two layers of film, usually Kapton, a substrate or base film plus a cover film, and the resistance foil (Constantan alloy) is sandwiched inbetween. The most common total thickness is about 50 microns, or roughly 0.002 inches. That's about half the thickness of 20 lb bond typing paper before you include the glue. The wires are much thicker than the gauge itself, and the connector is much thicker than the wires, which may comprise the main obstacles to attaching them to some guns.

Typically you would just glue the gauge over a tight spot and let the rest be where the space wasn't critical. However, there's a caveat: the gauges need a thin glue line, so they are typically pressed into place by rolling from one end using a silicone rubber or other release material over top of them to get a bubble-free thin glue layer. Simply sliding them into a tight space won't do. So, disassembly of the gun may be required.


I did some searching on the Castboolitz forum and found there are some plots of black powder pressure in shotguns available. From the discussions, one of the points made is that BP has an upper burn rate limit and thus, as the bullet scoots down the tube expanding the volume, the powder is still making a lot of its gas. This means a larger portion of the bullet acceleration is post-peak acceleration than is the case with a quick smokeless powder. Also, the combustion of black powder produces something like 58% solids and 42% gases. So, the difference in energy content in the two types of powder is not as large as the charge weight differences, with the BP simply producing much less efficient transfer of its energy to kinetic energy in the bullet by gas pressure than the fast smokeless powders do.
 
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