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Discussion Starter #1 (Edited)
Was cleaning out email and saw an email from Grabagun for a revolver that shoots 9mm or 357/38. I know 38 and 357 are the same diameter bullet that has separate cylinders for the 9mm or the 38/357 BUT is the diameter of a 9mm bullet the same as a 38/3257 or is it simply "close enough". The revolver uses the same barrel which is what raises the question. The gun is a Taurus BTW (quit laughing). I know cleaning kits for 9mm also work in 38/257 fur cleaning stuff isn't the precision of a bullet going down the barrel.

I would think one bullet would be a little smaller in diameter and thus lose a portion of the power.

Educate me please.

https://grabagun.com/taurus-31.html?utm_medium=Email&utm_source=ExactTarget&utm_campaign=Daily Email

Just found this

"Despite its name, the caliber of the .38 Special cartridge is actually .357 inches (36 caliber/9.07 mm), with the ".38" referring to the approximate diameter of the loaded brass case."

AND

9mm = .354331 inches.

AND

"A .38 Special bullet and a .380 bullet are not the same diameter. ... A .380 bullet is, however, the same diameter as a 9mm Parabellum bullet. Oh, and a .38 Special bullet is the same diameter as a .357 Magnum bullet, which is named for its exact diameter."

So a 38 Special = a 357 but not a 9mm while a 380 does equal a 9mm.

STOP

Just found this which shows a 357 bullet is the SAME (almost) as a 9mm
357 = .357 inches = 9.1 mm
9mm = .355 inches.

I know the casings are different so the cylinder must be made to handle the difference.
 
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Well it should also shoot .380 also. After all a 380 is also a 9mm:D

rounding errors from millimeters to "caliber"

.001" variance, lots of folks lose sleep on "slugging" revolver barrels to find the exact fit of lead bullets and neglect the human facor in shooting. Then there is all the issue of "leading"? lead hardness vs velocity

Essentially they are the same give or take .001" or 0.0254mm!!
 

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9mm 38 special calibers.png

https://en.wikipedia.org/wiki/Caliber

Answered your own question... I have a Ruger New Model Blackhawk with 2 cylinders - one for .38/.357 and the other for 9mm. The 9mm sits in the chambers not needing moon clips I believe because the cartridge is slightly tapered and/or sits on the leading edge of the casing. With the 9mm's in it, it's a pure joy to shoot.

BTW I believe I read somewhere (it's not in the chart) that .38 S&W (aka .38/200) are .354 diameter...
 

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I think you already figured out the bullet diameter thing: .380 & 9mm are the same diameter & .38 & .357 slightly larger so the smaller bullets will fit safely down the larger barrel. Then things get more complicated, 9mm cases are slightly tapered & wider @ the base than .38/357. .380 are not tapered & don't fit well & usually won't even fire in a 9mm or .38/357 chamber. The .380/9mm's don't have rims so won't extract from a revolver unless moon clips or in a single action. A while back I started a thread where I took a .357 Cimarron SA revolver & tinkered w/ reamers to make a gun that will shoot .38, .357, 9mm, .38 S&W, .38 short Colt &. 38 long Colt out of the same cylinder. It works but only if the ammo is made or reloaded to extremely tight specs. The chambers must be exact or some rounds won't fire or won't eject. I doubt Taurus is capable of making such a gun function properly since their quality is terrible.
 

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Discussion Starter #6
Thanks to all for the feed back. Thank you Injunbro for the info.

I kept looking as you can see in the op and found my answer but even then it raised some questions so I left it for me and others to learn. Learning is always good.
 

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To me the OP question was about the "Bullet", projectile. Not the actual cartridge and the dimensions of those different cartridges.

Was cleaning out email and saw an email from Grabagun for a revolver that shoots 9mm or 357/38. I know 38 and 357 are the same diameter bullet that has separate cylinders for the 9mm or the 38/357 BUT is the diameter of a 9mm bullet the same as a 38/3257 or is it simply "close enough". The revolver uses the same barrel which is what raises the question. The gun is a Taurus BTW (quit laughing). I know cleaning kits for 9mm also work in 38/257 fur cleaning stuff isn't the precision of a bullet going down the barrel.

I would think one bullet would be a little smaller in diameter and thus lose a portion of the power.
 

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So... as you swap and substitute components, realize that you're performing an experiment. That experiment is dealing with metal and gas pressures of 35,000 to 65,000 pounds per square inch or so.

When a firearms manufacturer sells a gun in the United States, they typically certify the firearm as complying with standards published by the SAAMI industry group. It means that the manufacturer has tested the firearm with the appropriate proof pressure ammunition in a series of measured experiments. When Taurus ships multiple cylinders for their revolver, they have done this.

A few thousandths of an inch in a barrel diameter has quite an impact over a number of interrelated things. This includes the bullet engagement into the rifling as it cuts through the barrel's rifling leade, the gliding surface of the bullet (including it's length and metal composition), and the overall friction encountered as it travels the length of the barrel.

What happens during the instant when a bullet that is too small tries to engage in the leade of a barrel that is too large? Is the engagement uniform? Does it hit one leade before slamming into the others? Does it twist or tumble slightly? Does that lack of uniform engagement increase the resistance to entering the rifling? Does it fly with stability coming out of the barrel?

I can assure you, as a human you cannot perceive the pressures involved using your senses. "It seems to work" does not mean it's safe.

The only way to be sure it's safe is to carry out measured experiments using technology that can sense, measure and document pressures.

Most of us don't own this kind of equipment.

As to cartridges fitting into different cylinders, all this comes down to headspace, and where the cartridge headspaces. A 9mm Luger cartridge doesn't depend on it's taper for headspace. It headspaces on the mouth of the cartridge case, and any cylinder designed for the the cartridge will have a ridge at the appropriate point in the cylinder to stop it from moving forward. The real problem is ejection. What exactly would a cylinder component grab onto to jerk spent cases out of the cylinder?

.38 Special and .357 cartridges headspace on the rim at the rear of the cartridge. The star wheel ejection mechanism works easily with this style of headspace. This is why moon clips and similar designs are used with rimless cartridges in revolvers.

Reloading manuals are not recipe books. They are documented evidence of controlled and measured experiments fired using specific components and a specific firearm barrel. When you deviate from the manufacturer's experiment, you'rd performing your own experiment - and in most cases without the benefit of instruments to measure the results.
 

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"As to cartridges fitting into different cylinders, all this comes down to headspace, and where the cartridge headspaces. A 9mm Luger cartridge doesn't depend on it's taper for headspace. It headspaces on the mouth of the cartridge case, and any cylinder designed for the the cartridge will have a ridge at the appropriate point in the cylinder to stop it from moving forward. The real problem is ejection. What exactly would a cylinder component grab onto to jerk spent cases out of the cylinder?"


The above is correct for semi autos and rifles but for revolvers non rimmed cases like a 9mm require a moon clip and there is no headspace involved in the revolver cylinder. shorter cases like a 380 in a 9mm or 40 in a 10mm(semi auto) will often headspace on the extractor
 

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I bought the Ruger New Model "Convertible" 38/357/9mm single action revolver and immediately had the 9mm cylinder rebored to 357/44 Bain & Davis.
Pretty potent cartridge that went with me to Africa as part of a 3-gun battery on a "Handguns Only" hunting trip.
 

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The reason the .38 Special is call a 38 is because the original loading was the same style as the .22 caliber round with the exposed portion of the projectile being the same diameter as the brass case and the base of the projectile being of a reduced diameter to fit into the shell. I believe that the .22 cartridge is the only modern round to retain this feature.
 

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"Despite its name, the caliber of the .38 Special cartridge is actually .357 inches (36 caliber/9.07 mm), with the ".38" referring to the approximate diameter of the loaded brass case."
That's not right. The first ".38" cartridges actually used a .38 inch bullet of a "heel" type where the bullet diameter was the same as the outside diameter of the cartridge case and had a reduced diameter "heel" that fit inside the case. You still see this type of bullet in .22lr rounds.

Later, the bullet was redesigned to fit completely within the cartridge case by eliminating the heel and reducing the bullet diameter to match. That's why current ".38" rounds use a .357" bullet but the 38 name persists.

The same history applies as to why .44 rounds use a .429" bullet.
 

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View attachment 380777

Caliber - Wikipedia

Answered your own question... I have a Ruger New Model Blackhawk with 2 cylinders - one for .38/.357 and the other for 9mm. The 9mm sits in the chambers not needing moon clips I believe because the cartridge is slightly tapered and/or sits on the leading edge of the casing. With the 9mm's in it, it's a pure joy to shoot.

BTW I believe I read somewhere (it's not in the chart) that .38 S&W (aka .38/200) are .354 diameter...
Yes, 9mm indexes on the leading edge, but it also does not need moonclips to eject. Blackhawks eject from the front. You can do the same with double action revolvers also, not using moonclips and ejecting from the front (with a pencil or something)
I want one of those Blackhawks really bad by the way. Awesome in 357/9mm
 

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I think you already figured out the bullet diameter thing: .380 & 9mm are the same diameter & .38 & .357 slightly larger so the smaller bullets will fit safely down the larger barrel. Then things get more complicated, 9mm cases are slightly tapered & wider @ the base than .38/357. .380 are not tapered & don't fit well & usually won't even fire in a 9mm or .38/357 chamber. The .380/9mm's don't have rims so won't extract from a revolver unless moon clips or in a single action. A while back I started a thread where I took a .357 Cimarron SA revolver & tinkered w/ reamers to make a gun that will shoot .38, .357, 9mm, .38 S&W, .38 short Colt &. 38 long Colt out of the same cylinder. It works but only if the ammo is made or reloaded to extremely tight specs. The chambers must be exact or some rounds won't fire or won't eject. I doubt Taurus is capable of making such a gun function properly since their quality is terrible.
You buried the lead.

The last sentence would have been better served up first for the benefit of the OP.

Hope he didn't miss it.

:D
 
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