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Old November 25, 2008, 05:11 PM   #1
jughead2
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38 short

i have in my possession a smith in 38 short would it be possible to change cylinder to 38 special??????????
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Old November 25, 2008, 05:16 PM   #2
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This depends on what firearm you have, but the simple answer is NO. 38 S&W Short operates at very low pressure, and most firearms chambered for it would not tolerate the higher pressures of a 38 Special. 38 Special is also probably longer than the cylinder of the gun you have. Good news is that you can still buy factory-loaded 38 S&W ammo.
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Old November 25, 2008, 08:38 PM   #3
jughead2
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38 short

thanks for the reply. cylinder is long enough. barrel says 38 767. 3 1/2 tons. ???????????????
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Old November 25, 2008, 11:20 PM   #4
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It may be a somewhat collectible S&W... It might be a good idea to check before taking any chances. Other than that, you can reload for it. I checked case dimensions in the Lyman 47th to see if you could just trim 38 Spl cases and load them as 38 S&Ws. The specials are a few thousandths smaller so I don't know. Just a thought though.
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Old November 25, 2008, 11:36 PM   #5
Jim Watson
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Quote:
38 767. 3 1/2 tons. ?
Means it went to England.
Calibre is .38, case length is .767 inch, and British proof test pressures are given in long tons per square inch.
It is probably a Victory Model or an earlier Lend-Lease revolver from WW II. The British went to .38 S&W to replace the .455 Webley about 1928. The official issue was an Enfield top-break revolver that looks a lot like a Webley, but they needed all the guns they could get when WW II broke out and they used large numbers of real Webleys and Smith & Wessons. Smith & Wesson owed them a lot of money after the failure of the S&W Light Rifle project anyhow, and convinced them to take guns instead of cash.

If it is in good unaltered un-refinished condition it is worth a bit of money. Thousands of these guns were rechambered to shoot .38 Special after a fashion so they would sell better as surplus back in the U.S., and many were sawn off to fake snubbys. The ones that remain are of collector interest. If not messed with.
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Old November 26, 2008, 05:13 AM   #6
jughead2
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38 short

thanks guys. there is more knowledge on this board than this old man could ever use. guess i will keep it it is unaltered.
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Old November 26, 2008, 08:05 AM   #7
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Assuming the British were still using imperial tons at the time, that proof level is just 7,840 PSI. SAAMI puts the .38 S&W maximum at 17,000 PSI, same as they do the .38 Special. The latter just has more powder capacity to let it reach higher velocity for a given peak pressure. I've no idea what the British were up to with that 3.5 ton proof load choice?

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Old November 26, 2008, 01:01 PM   #8
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Actually, the marking is not for the proof load pressure, but the cartridge mean working pressure, and that figure is about correct. If the gun is an S&W M&P ("Victory Model"), it was made in .38 S&W for the British and .38 Special for the U.S., so it is perfectly capable of handling standard .38 Special pressures (not +P or +P+).

SAAMI proof pressures are assuming modern guns. I guarantee that many old iron guns made for .38 S&W would come apart at 17k psi, and the cartridge is not factory loaded to even half that pressure level.

Conversion of a .38 S&W M&P model (Model 10 later) to .38 Special is not recommended as accuracy is poor and there may be extraction problems with swolen cases, but there is little danger and hundreds of thousands were converted. The collector value, as already noted, is adversely affected by such a conversion, though. Conversion of any other .38 S&W caliber revolver, such as an old breaktop or inexpensive solid frame revolver would either be impossible or dangerous.

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Old November 26, 2008, 04:14 PM   #9
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Many .38 short (or .38 S&W) guns were made in the days of black powder. If that's the case with your gun, even shooting smokeless ammo in it might be a real bad idea.

I inherited 2 old break-top .38 S&W guns from my grandfather. One was an Iver Johnson and the other was an H&R. The 3rd cylinder of smokeless ammo through the H&R blew it up. The top chamber blew, the topstrap bent, the latch broke and it popped open, ejecting the unfired ammo and empty cases. No damage to me, but that little gun was toast.

I shot black powder reloads in the Iver from then on.
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Old November 27, 2008, 12:26 PM   #10
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Jim,

That makes more sense. It's for Cowboy Action level loads. I expect lead bullets and Trail Boss would be a safe smokeless combination.
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Old November 27, 2008, 09:07 PM   #11
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You cannot just apply a conversion factor of long tons per square inch times 2240 equals pounds per square inch. The British pressure test method was entirely different. They used an axial pressure gun with the crusher under a floating bolt head. It gives a lower numerical reading than the US radial crusher gauge for the same load. So their ratings sound low to us, but there is no real difference in the ammunition.
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Old November 27, 2008, 09:23 PM   #12
jughead2
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38 short

i compared it to a 38 cylinder and they look the same. i know it takes more than looks but if the special cylinder will fit looks like it would work. do not want to hurt me or the weapon. it is not something that has to be just a curious old man.
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Old November 28, 2008, 08:17 PM   #13
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Unfortunately, you can't just "drop in" another cylinder.
Cylinders are VERY much fitted and adjusted items, and the person doing it needs to be a very experienced gunsmith who knows cylinder work.
Unlike most automatics, most critical parts of a revolver are hand fitted at the factory, and you can't simply drop other parts in and have them work properly.

Among others, the following must be fitted and gaged on cylinders:
Head space.
Barrel/cylinder gap.
Cylinder end shake.
Barrel/chamber alignment on all 6 chambers.
Timing.

Best to leave your revolver as-is then ruin it trying to improperly install another cylinder.
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Old November 29, 2008, 10:54 AM   #14
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Jim W,

The SAAMI maximum data I cited was for Piezo transducers, and not crushers, but I didn't bother to mention that because those different systems tend to be close at lower pressures. That happens because all pressure measuring systems converge at zero. U.S. Piezo and CIP Piezo and US copper crushers and CIP copper crushers all read differently at high power rifle pressures, but tend to be pretty close below 30,000 PSI. I assumed that would be true for the British measuring system too, but confess that I don't know at what pressures it's readings diverge significantly from the other systems? It might make for some interesting historical research? I have a pretty good chart for absolute pressure v. copper crusher in the .30-06 done at the U. of Michigan in the mid 60's, but have yet to find equivalent quality information for other rounds or other measuring systems.

I also found a disagreeing reference on the SAAMI pressure for the .38S&W. One has it at 17,000 CUP and 17,000 PSI, both separately listed, like the .38 Special, while another has it at just 12,000 CUP, that number listed alone. So it looks like I need to go to the horse's mouth on that one to see which is correct and whether it has changed over the years? I can't imagine they would raise it on a round mainly fired in older guns.
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Old November 29, 2008, 01:48 PM   #15
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How about a third number? Accurate Arms says the SAAMI maximum average chamber pressure for .38 S&W is 13,000 CUP. It may be that 17,000 is the absolute maximum individual pressure reading. Those things are not as accurate as they would have us think.

The British axial crusher system is significantly different to US radial crusher or anybody's transducer. Gough Thomas compared all available shotgun loads and reload data and concluded that a British ton per square inch was equivalent to about 2800 US LUP in that application. Rifles and pistols, who knows? I don't know if the British are using CIP now or if they still follow their own system.

Last edited by Jim Watson; November 29, 2008 at 01:55 PM.
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Old November 29, 2008, 07:41 PM   #16
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FWIW, the British have officially gone to Bars. I doubt the actual real proof pressures have changed but, as I said, the marking never was the proof pressure, but the standard working pressure.

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Old November 29, 2008, 09:18 PM   #17
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Bars are what the CIP Piezo system is given in. My understanding is they locate their transducer gas sampling point near the case mouth which causes it to be a couple thousand PSI lower than the SAAMI mid-web readings on the same cartridge in bottleneck rifle rounds. But you'd never know it looking at their numbers. Some are higher and some are lower than U.S. numbers. I agree these absolutes can have somewhat iffy value in determining what is safe in a particular gun. I think any of us who've been shooting for awhile have occasionally seen commercial or military ammo that was too hot, and much more often that was pretty lame, relative to safe potential for the cartridge. Mostly these measuring systems are useful in the industry for adjusting charges of different lots of non-canister grade powders to produce matching peak pressures, and to keep lawyers satisfied.
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Old November 30, 2008, 10:46 AM   #18
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The "bar" is a unit of pressure commonly employed by foreigners and the weather bureau. It does not define the method or equipment used to measure it. It just happens that the usage came in about the time that piezoelectric chamber pressure transducers did.

One bar is 100,000 newtons per square meter. It just happens that standard atmospheric pressure is a little over one bar which makes it convenient for the weather bureau to figure in millibars.
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