# Caliber interchange question (CAUTION: NOOB!)



## IntegraGSR

I've seen several posts here and on other forums about being able to use .38 ammo in a .357... Could someone educate me here, since I'm thinking that the number refers to the bullet diameter in inches (.380" and .357" respectively). If a barrel was .357" in inside diameter, technically a bullet that's .38" in diameter would be a EXTREMELY press-fit into a .357" hole. What gives? Please forgive the n00b question, but I'm trying to broaden my firearm knowledge!


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## James NM

The .38 ammo you are referring to is called ".38 special". It is actually .357 in diameter, same as a .357 magnum. Thus, you can shoot .38 special in a 357 magnum revolver. The difference between the two is that the .357 magnum case is longer than the .38 special. But, you cannot shoot .357 magnums in a .38 special revolver.


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## PhilR.

One additional difference is that besides having a longer case, the .357 has a much more powerful load as well - high enough that most .38's cannot withstand. The additional case length is a kind of safety factor which prevents someone from blowing up their revolver.

Caliber nomenclature is not an exact science. The official designation of any particular caliber can be a number that is more or less "rounded off", so to speak. Sometimes this is done to make a differentiation between two similar bullet diameters, such as seen in the .38/.357....

PhilR.


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## Bob Wright

While you are correct that the numbers DID indicate bore diameter, that is no longer really the case. Practices over the years have changed so that the caliber designation is only a relative reference.

Example: The .38 Special has a bore diameter of .357"

The .38-40 and .41 Colt bore diameter is .401"

The .44 Russian, .44 Special, and .44 Magnum bore diameter is .429"

Its a long story in cartridge developement, but originally, with heel crimped bullets, bore diameter was closer to caliber designation. Then, with the elimination of heel crimped bullets, bullets became smaller in diameter than bore diameter specifications.

Know this is clear as mud.

Bob Wright


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## Bob Wright

And, never hesitate to ask questions. It gives us know-it-alls a chance to expound from our great wealth of knowledge.


And, you just might learn something.

Bob Wright


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## Bob Wright

And, as a matter interest, a .357 Magnum revolver can digest .357 Magnum, .38 Special, .38 Long Colt, and .38 Short Colt. Not recommended, but in a pinch, also .38 Super, .38 ACP and .35 Winchester Self Loading. In fact, the .35 WSL was one of the cases considered in the developemnet of the .357 Magnum cartridge back in 1935.

Bob Wright


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## Liko81

Yep, they've pretty much covered it. .38 Special was designed as an improvement over the .38 Long Colt (the much maligned round of U.S. Army troops in the Phillipine insurrection). Both .38 Special and .38 Long Colt have a bore diameter of .357", in contrast to the original .38 cartridge known as .38 Short Colt which has a bore diameter closer to .38". The .357 Magnum was an improvement on the .38 Special; higher pressures, bigger bullet, more stopping power. Because the bullet exceeded the design limits of .38 revolvers, it was made longer so it wouldn't fit in an ordinary .38 revolver, however, the shorter .38 will fit into a .357 magnum revolver just fine and the revolver can easily handle the lighter load. There are a few other revolver cartridges that work the same way. .22LR, for instance, has the .22 Hornet and .22 Short as common cousins. In most revolvers, these are interchangeable (autoloaders and repeaters are pickier about the case length and the OAL). .44 Special and .44 Magnum work exactly the same way as .38/.357, and .454 Casull revolvers will accept a .45 Long Colt cartridge.


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## IntegraGSR

Thanks guys, I appreciate the info!


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## No786

Same size outer diamiter. 
The .357 is just longer.
You can only go to .38 if you have .357, many do this for target because .38 is cheaper!


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## Don357

Just to confuse you more, with the proper cylinder a .357mag/.38spl can also fire a 9mm Para or .380 which have a bullet diameter of .355mm.


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## Bob Wright

Don357 said:


> Just to confuse you more, with the proper cylinder a .357mag/.38spl can also fire a 9mm Para or .380 which have a bullet diameter of .355mm.


Depends on the cylinder/gun. In the Ruger Blackhawk, clips don't work, and the .380 wouldn't headspace correctly, being a shorter case. The short case would require half-moon or full-moon clips in order to headspace.

Bob Wright


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## tony pasley

Bob Wright said:


> And, as a matter interest, a .357 Magnum revolver can digest .357 Magnum, .38 Special, .38 Long Colt, and .38 Short Colt. Not recommended, but in a pinch, also .38 Super, .38 ACP and .35 Winchester Self Loading. In fact, the .35 WSL was one of the cases considered in the developemnet of the .357 Magnum cartridge back in 1935.
> 
> Bob Wright


Bob you left out the 9mm with half-moon clips.


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## Bob Wright

tony pasley said:


> Bob you left out the 9mm with half-moon clips.


You can not use half moon clips in a revolver that has not been relieved for them, that is, you can not simply clip three 9mm rounds into a clip and load it into a .357 Magnum revolver.

The single action revolver, such as the Ruger Blackhawk, can be had with 9mm cylinders and this readily exchanged with the .357 Magnum cylinder. The same is true for the Smith & Wesson, though changing cylinders is not quite so easily performed. Note that in the Ruger, clips are not required, as the rod ejector handles the job of ejection easily, and the cylinder is chambered for the 9mm round's length.

To reiterate what I've said, the cartridges I named, various .38 Special, .38 Colts, .38 ACP and .38 Super, can be fired in a .357 Magnum cylinder. The .38 ACP and .38 Super are semi-rimmed cartridges, though I think the .38 Super may now be rimless, and would headspace on the tiny rim. The 9mm Parabellum, or Luger, is rimless and must headspace on the case mouth. Same is true for the .380 ACP, which would drop too far into the chamber for correct headspacing in a 9mm chamber.

In 9mm, only cartridges such as the 9mm Glisenti would fire in a 9mm Luger chamber. IF the gun were made to accept half moon clips, then shorter cased cartridges could be used.

With the exception of .38 Specials in .357 Magnums, the obvious best thing to do is use ammunition stated on the gun's barrel. These other variations are purely academic or emergency in nature.

Bob Wright


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## Bobmotomo

Bob, does the bullet diameter of the 9mm lessen accuracy of the Ruger Blackhawk Convertible ?


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## Argon18smith

Lots of info for sure. It just crossed my mind, what about brass thickness for different pressure or is that a non-issue as long as everything is secured inside the chamber? I am tinkering with reloading 38 specials beyond the +P loads for use in my 357 magnum.


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## tony pasley

Any time you are reloading beyond specs. you are taking a chances the farther out of specs, the greater the chances. I personally don't recommend it.


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