Max psi in 1905 hand ejector

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solman

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Heres the weapon/ 1905 hand ejector target made in 1913. im loading with hs-6 5gr at 14000 ish psi. 148gr wadcutter. whats max pressure on this weapon. some solid number i can work with.
ive looked on the net and i get all kinds of different answers?!!
can you help??????? oh one ragged hole at 15 yards.
 

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Nice specimen of a pre-WWI M&P with adjustable sights. There aren't that many of those.

I don't shoot anything other than 148gr wadcutter target loads in my S&W .38s from the 1920s and before, so my personal pressure limit is in the vicinity of the 14,000 PSI you mentioned. One regularly hears the assertion that any modern standard .38 Special load can be fired safely in these older guns, but that +P and definitely +P+ loads should be left alone. That rule of thumb maxes you out around 17,000-18,000 PSI.

But to offer a possibly unwelcome opinion, I am not sure I would be experimenting with a gun that old and that collectible to see how hot a target load I could develop that wouldn't damage it. For me, you are at the "wise" as opposed to clinical max right now with the loads you mentioned, even if someone calculates that the steel is good for pressures 20-30% higher than that.
 
I'll jump on the lower pressure bandwagon. with my older revolvers I keep the pressures low and only use lead bullets. Why beat them up when I have more modern revolvers for that sort of thing.
 
thanks folks!! Im with you on the pressure thing. IMHO if you go maxing out the pressure playin elmer keith you will pay. ive never had one blow up, but ive passed on a couple nice BP handguns i thought were 'loose'.. this one was 'new in box'.. when i took off the grips to check there was NADA wear on the guts. and if i keep lead only bullets and pressure less than say 15k i could shoot this forever. and im my experience with the older weapons you can load or get some standard pressure lead hollow points for protection/hunting. ( i have buffalo bore 158gr hollow point semi wadcutters for that) but only for that.
the reason i asked is powder is hit and miss. i now have some 700x i just got. the HS-6 is great! but sooty at this low a charge. i keep a brush handy as the pistol is so tight any gumming results in fail to lock cylinder. but man! the most accurate pistol ive ever owned, beating out a (who would guess) a rust bucket Nazi p-38 i once owned.
so ill keep under say 15k and good to go. i go to 15 yards and under for the 'grouse shot' with this baby i can do a head shot. its just amazing!!
thanks again!!
P.S. the original grips are in my safe!!!
Sol
 
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I will now get on my soap box and vent a bit! I keep reading advice to use target wadcutters and no jacketed loads in older guns in .38 special, but if you go to the SAAMI specifications, you will find no differences in the pressure limits for wadcutters and standard service loads, and no difference between jacketed bullets and lead bullets. The commercial ammo manufacturers are in business to make a profit, and to do that will use the smallest charge of the cheapest powder that will provide that result and stay within the maximum average pressure limits. Unless you have access to the pressure data for the particular lot of ammo, there is absolutely no way to be sure that a paticular lot of target ammo is not in fact higher pressure than a particular lot of service ammo. You can be sure that ammo from one of the major companies will adhere to the SAAMI standards and service or target ammo will be safe for any US firearm originally chambered in that caliber, provided that the firearm is in good condition. Any reloading data used should have pressures listed that do not exceed the SAAMI pressure limits for service or target ammo.
 
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I would you had rather ask what the minimum pressure that you can get away with??:D. That is a great old target gun that has been around a long time and you should make sure that it is around for many more decades to come. I load to velocities under 700 fps and never need to worry about max anything. If you are punching holes in paper, 650 fps will do the job with little recoil and little stress on the gun. To achieve those pressures, I use high bulk powder and usually load 158 grain semi-wadcutters. You can usually get lower velocities by loading about 80 - 90% of the lowest loads listed in reloading manuals.

One example I load is 158 SWC with 2.5 grains of Trail Boss. That load gives about 650 fps and 10,000 psi and is very accurate out past 25 yards.
 
solman said:
. . . when i took off the grips to check there was NADA wear . . .
Click to expand...

That reminds me to let you know those Magna stocks are about 60 years newer than the gun. Depending on the serial number range, the proper stocks should be round top diamond walnut service stocks. There were concave, medallion, and convex top stocks depending on what decade your revolver was made. Ebay often has toes K frame stocks for sale and some in very good condition if you keep watching.
 
glowe said:
That reminds me to let you know those Magna stocks are about 60 years newer than the gun. Depending on the serial number range, the proper stocks should be round top diamond walnut service stocks. There were concave, medallion, and convex top stocks depending on what decade your revolver was made. Ebay often has toes K frame stocks for sale and some in very good condition if you keep watching.
Click to expand...

He said he has the original Stocks in his Safe.
 
"...you will find no differences in the pressure limits for wadcutters and standard service loads, and no difference between jacketed bullets and lead bullets."

The peak chamber pressure limits are maximums as established by SAAMI, not the individual ammunition factories. Compliance with SAAMI standards is voluntary, but most US manufacturers will comply closely with them. In general, actual production ammunition is almost always held somewhat below the SAAMI pressure limits. I know for a fact that by piezo pressure gauge measurements, .38 Special factory 148 grain full wadcutter bullet loads are typically loaded to a peak pressure around 8,000 psi. Other loads may well have somewhat higher peak chamber pressures, but all will be below the SAAMI limit for the caliber. Factories try to load each cartridge type to a uniform lot-to-lot muzzle velocity standard which is well within the SAAMI pressure limits. That may require minor changes in propellant charges to achieve a standard MV, depending upon the production lot of the powder, as there are slight lot-to-lot variations. That's one of the main purposes of a factory ballistics lab, to test the chamber pressures and velocities for each cartridge caliber for each lot of powder before a production run is started.

It's nothing more than an illusion for any handloader to assume he can load to some given peak chamber pressure, unless he has the expensive pressure measurement equipment needed to measure it himself. Few do, outside the factories.

"I think the use of Lead Bullets is more for the wear on the Barrel than the increased pressures."

That is correct. During WWII (in May 1942), S&W did change the steel alloy used for barrels from AISI 1025 to AISI 1045 to provide more wear resistance. Military .38 Special ammunition has steel jackets, which would increase bore wear substantially.
 
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DWalt said:
....It's nothing more than an illusion for any handloader to assume he can load to some given peak chamber pressure, unless he has the expensive pressure measurement equipment needed to measure it himself. Few do, outside the factories....
Click to expand...

Excellent point. The complete list of variables that affect chamber pressure is beyond the scope of even most advanced home handloaders. One thing that needs to be understood is that most pressure data published by ammo manufacturers is measured in test barrels which have virtually no resemblance to anything we'll ever hold in our grubby little hands. Chamber and bore dimensions are held to much tighter tolerances than the SAAMI minimum +.002" tolerance used by sporting arms manufacturers.

Also, older loading manuals have chamber pressures listed in C.U.P. (Copper Units of Pressure) which can not be accurately translated or extrapolated to P.S.I. readings - which are taken via the more modern piezo method.

Mark
 
wheelgun610 said:
. . . Also, older loading manuals have chamber pressures listed in C.U.P. (Copper Units of Pressure) which can not be accurately translated or extrapolated to P.S.I. readings - which are taken via the more modern piezo method . . .
Click to expand...

Mark, that is not entirely true. An often quoted source has extrapolated CUP to PSI comparisons. In 2002 a study was made to generate direct comparisons, including a reference chart. Bottom line of the study was that most standard handgun pressures are in the lower end of the charts and the differences between the two numbers show no variations between CUP and PSI up to 20,000 PSI. When you get into the upper range of pressures that mostly are found in rifle calibers, the differences become larger and are worth noting. Since I rarely exceed 10,000 psi on any of my vintage revolvers, I don't worry too much about whether I am reading CUP of psi numbers.

Interesting study can be found at: https://www.shootingsoftware.com/ftp/psicuparticle2.pdf

The chart below is a interpretation of the work done in the study.
 

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Generally, there is no good way to make a comparison between CUP and actual piezo gauge chamber pressure measurements, because CUP is in fact not a pressure measurement at all. Rather it is something analogous to a pressure measurement, namely the amount a copper pellet is crushed under the pressure of firing. It should be considered only as an analog indicator of pressure, not a pressure measurement. It is a very old method, dating from the days long before anything electronic existed. The general assumption is that actual peak chamber pressure (in PSI), as measured by a piezo gauge according to SAAMI methods will be up to 20% greater than a copper crusher determination (in CUP) under the same conditions. In effect, the CUP is an indicator of a sort-of "average" chamber pressure, as it has a much longer response time, vs. the piezo gauge's near-instantaneous (microseconds) response time. The chart provided above has the axes labeled as CIP. CIP is a European standards organization and uses a pressure test method which is somewhat different from the SAAMI method, although both use piezo gauges. I know of no ammunition manufacturers which today continue to use the copper crusher method, as the piezo gauge method, in widespread use since about 1970, is much faster, simpler, and far more precise than the copper crusher method. It also allows measurement of pressure vs. time, which the copper crusher method cannot. I have been in about every manufacturer's ballistics lab, and several military labs, and there are no copper crusher barrels in use. However, SAAMI still recognizes the use of both methods at present.
 
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So what are your comments on the report? I am always digging for data and, so far, this seems to be the best correlation I have found.

Denton Bramwell, the guy who did the CUP vs PSI study certainly has some good credentials for writing about pressure testing.

"Denton Bramwell is a regular contributor to Varmint Hunter Magazine. His continuing series of articles in Varmint Hunter about load pressure issues are some of the best we have seen. Mr. Bramwell is a physicist and statistician with a background in measurement instrumentation. His conclusions are always supported with good data and proper analysis. When not shooting to gather data for another Varmint Hunter article, Denton is consulting with design engineers."

At least that is what the bio says. His conclusion is that PSI is highly correlated to CUP.
 
There is no doubt that there is correlation between CUP and PSI, as all correlation means is that if one value changes, so does the other, and in the same direction. The real problem is universality of the conversion. While there may be a very close relationship (i.e., a high coefficient of correlation) between CUP and PSI for a given cartridge with a given propellant and a given charge, when you change the cartridge and propellant and charge, the formula expressing the CUP-PSI correlation changes. This is because PSI is an absolute value, while the degree of crushing of a copper cylinder is not. So you cannot reliably define the CUP-PSI relationship for every circumstance by using the same formula.

Let's use the equation for a simple linear relationship between two quantities, X (CUP) and Y(PSI) which is Y = MX + B. You can then compare the peak chamber pressures of, say, the .220 Swift by each method, finding that to get the highest correlation coefficient, M=1.2 and B=1000. Well and good - you have established a conversion relationship, and it likely can be used for similar cartridges of similar case volumes and pressures.

Let's repeat the experiment using a .38 Special cartridge. But this time, you find that the highest correlation between CUP and PSI results in M=1.0 and B=300. It then becomes obvious that you cannot use the correlation equation that works so well for the .220 Swift for the .38 Special (or vice-versa) and expect realistic results. But the .38 Special CUP-PSI conversion equation might be fine for comparing different .38 Special loads.

This is why measuring an absolute value of chamber pressure is so superior to using a copper crusher, simply because PSI is always PSI, no matter what cartridge you are testing. The piezo gauge always responds the same to chamber pressure for every cartridge. The copper crusher does not due to differences in expansion ratio and propellants.
 
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