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Recently acquired an 1892 38-40. Cleaned it up some and bought a box of Winchester ammo. Shot it today and 2 of the 5 cases have ruptured at the shoulder. Any idea why. And why didn’t all of them rupture?
 

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The Troll Whisperer (Moderator)
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You are working with a very thin wall case to start with. Rupturing at the shoulder may indicate a chamber problem, even with the rimmed case. Murphy's Law says you got lucky with the 3 other cases.
 

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You would be better served to have a gunsmith analyze your problem. Asking this forum without anyone here being able to have a hands on look or even a picture will only bring you guesses & speculation. Last time I checked guesses & speculation don't fix much & can lead to things getting worse. Just my two cents!
 

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The Hog Whisperer (Administrator)
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How old was that ammo? Sounds like it got brittle with age. .38-40 generally doesn't run at extreme pressures.
 

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One fact about the .38-40 is that the factory cases are a very different shape than factory chambers; the neck is much longer. Compare your unfired cases to your fired cases and you’ll see the difference (see photo below). When fired the case shoulder is moved forward substantiallly, and this fireforming highlights any weakness in the brass. Too, a 126-year old revolver’s chambers may be even larger than current SAAMI standards, and not all chambers may have the same dimensions now. It isn’t common to get case ruptures in the shoulder area, but it isn’t rare either. Careful handloading new brass may be the best way to eliminate case ruptures.


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Measure the difference between un-fired and fired. The case is unsupported and so expands past its ability to conform so it breaks.
The barrel needs replaced or set back a turn but that means the mag tub has to be cut back, too. It's a PITA because the extractor cut has to be deepened, too.
 

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So far we have several theories. One is that the case walls are thin to begin with & you may have a "chamber problem". Then it's possible that your ammo is old and "brittle". Next is the case dimensions & the chamber dimensions are "different". Finally, the barrel needs set back, the mag tube shortened, & the extractor groove deepened. Be patient, there will be more guesses & speculation coming. Everyone that responded did so in good faith & has the best intentions & everything they said has a possibility to be correct. The reality is you are no closer to resolving your problem than before you posted your question. I now refer you to post #3.
 

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There are no 'theories' when we see the picture that carp diem posted! There's the answer. The fire-formed case is WAY different than the unfired. With that much expansion in a low-pressure cartridge, the crimp can hold tight enough to jerk the case in half. 38-40 cases used to have a cannelure at the base of the bullet and it was common to break cases through that stress riser.

By measuring the fire-formed case, I think you'll find a chamber that won't 'clean up' even if the barrel is set back. Revolver cylinders are SOL.
 

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There are no 'theories' when we see the picture that carp diem posted! There's the answer. The fire-formed case is WAY different than the unfired. With that much expansion in a low-pressure cartridge, the crimp can hold tight enough to jerk the case in half. 38-40 cases used to have a cannelure at the base of the bullet and it was common to break cases through that stress riser.

By measuring the fire-formed case, I think you'll find a chamber that won't 'clean up' even if the barrel is set back. Revolver cylinders are SOL.
Being the pics are NOT of cases fired in the OP's rifle, how you determined "there's the answer" baffles me. Say by chance your guess is correct. Isn't he going to have to take it to a gunsmith anyway? All I'm saying is he should start with the gunsmith unless you can fix it remotely over the internet. I see you've changed your mind & are now saying the chamber can't be cleaned up even if the barrel is set back. So does that mean he needs a new barrel now? Which of your guesses is the OP to follow? Or should he wait till you come up with a third guess? Until you have that rifle in your hands, any analysis is mere speculation.
 

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There are no definite answers unless the gun is seen, measured, examined and analyzed, but 38-40 chambers (and many others) are many times 'large' in older guns, AS SEEN IN THE PICTURES ABOVE no matter where those pictures came from. That is a good example of what is found in many older model rifles shooting RIMMED cases. Anytime brass is asked to expand, there's a chance for breakage.
Measurements determine the path of repair. Until those measurements are taken, nobody knows anything but what mausernut reported.
 
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The Hog Whisperer (Administrator)
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Shooters fire-form brass all the time to much larger dimensions that what would be indicated in the photos. Brass is supposed to be soft and able to form to the chamber. It should be possible to blow the brass out completely straight if needed. Once in a while photos show up of a piece of brass that was clearly fired in the next larger chamber - ie. 9mm in .40 S&W, .40S&W in .45 ACP, and so forth, without the brass being split. Which is not to say it was a good idea, but it can happen.

Neck-size the cases that survive and move on would be my advice, and I'm still on the side of brittle brass causing the splits. Yes I'd like to see photos too. There have been articles I have read in the mainstream gun press about the need to neck-size, or minimally-resize, old cartridges like the .38-40 and .44-40 due to severe mismatches between oversized chambers and undersized reloading dies. The CAS crowd is well familiar with the thin walls of such cartridges. While first person examination would surely be more definitive, this isn't too difficult of a problem to track down, in my opinion.
 

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If we outlaw speculations, multiple choices and good guesses, we'll all have to sit and stare at a blank screen and do shoulder shrugs. ;)
This is more like taking calls by phone in the gunshop from the guy across town. (or from a lawyer across the country). Without seeing, handling, fondling, operating and analyzing by feel, sound and sight, it is all just a guess and until then the 'smith depends on good information and experience to give good answers.

My dad found a Model '73 full rifle in 38-40 in a rental house and brought it home. I was about five. By the time I was ten, I'd shot the rusted hulk one time, which pulled the case in half at the cannelure and put it (THANK YOU!!^^ ) out of service.
 

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Discussion Starter #15
I also just took this from Wikipedia.

One unusual design element of this cartridge is that factory ammunition was loaded with a different case profile than the standard chamber for this cartridge, factory ammunition having a much longer neck than the standard chamber. Most reloading dies are designed to size fired brass to the chamber specification rather than that of the original factory ammunition case profile.[3]
 

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No need to rechamber it. Just reload for it and only neck size the fired cases. Lots of older bottleneck cases were factory loaded to accomodate different chamber dimensions.
 

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You may consider doing a "chamber cast". This would provide an actual model of what your rifle chamber is. Using micrometers you can then measure what you have. Of course, if you have inside micrometers capable of taking these dimensions, that would also give you the data. Pending all of that, a good local gunsmith, familiar with the 92's, is also a very good option. Good luck with it. Bore
 

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Here is a picture of the cases. 1 with a rupture, 1 that didn’t and the factory ammunition. This is a rifle built in 1904.

The fired cases you posted have definitely had their shoulders blown out further forward than the unfired cartridge.

Before working on the rifle's barrel/chamber, I would buy some new/unprimed brass and fire case-forming handloads before using the fire-formed cases with "normal" loads - which is infinitely better (and less costly) than altering the rifle.



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I know this is an old thread, but...

I reload 38-40 and 44-40 with varied headstamps, Starline, R-P, Win. I have found the most ruptures and splits with Winchester brass. I don't keep track of the number of times reloaded, but the Winchester brass seems much thinner than the others, and could be a factor here.
 
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