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December 3, 2015
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Can anyone describe the dimensions of the cylinder bores and throats for the small frame .357?
The bore ( Charge hole ) where the cartridge sits must be a constant dimension from the case head to the case mouth as the .357 Magnum cartridge has a straight wall case. This would extend into the cylinder for the length of the case. This has to be or the cartridge would not fully enter the cylinder charge hole. This bore would be at or close to .379 inch.
What happens at the case mouth? Is there a "neck" that tapers directly to a narrower throat dimension? This throat dimension being a constant diameter to the muzzle end of the cylinder? Or is there a continuous gentle narrowing from the case mouth to the muzzle end of the cylinder forming the cylinder throat without a necked transition from initial bore?
Obviously the muzzle end of the cylinder has smaller bores than the firing pin end. What I am trying to visualize is just how this transition occurs. Probing the cylinder bore with a right angle probe produces no definite lip or transition area. Visual inspection would support this.
Anyone know the original production specifications for: 1) cylinder bore dimensions, 2) throat dimensions, 3) barrel bore dimensions, Either groove to groove or land to land?
March 22, 2016
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there is a tapered reduction in diameter from case o.d. to a smaller diameter, about .06" past the case length, pretty tough to see.. because it's so short.
Don't have small pin gages handy to tell ya the diameters tho.
there is also a relieved bore at the breach of the actual barrel, that coincides with the exit bore of the cylinder..then a tapered section leading to the full i.d. of the rifling.
as an addition, I have "faced" the rear ends of all of my bbls at one time or another, true them up and offer a fresh lead in and sealing area.
December 3, 2015
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man of blues said
there is a tapered reduction in diameter from case o.d. to a smaller diameter, about .06" past the case length, pretty tough to see.. because it's so short.Don't have small pin gages handy to tell ya the diameters tho.
there is also a relieved bore at the breach of the actual barrel, that coincides with the exit bore of the cylinder..then a tapered section leading to the full i.d. of the rifling.
as an addition, I have "faced" the rear ends of all of my bbls at one time or another, true them up and offer a fresh lead in and sealing area.
Thanks MOB.. I do not own any pin gauges so I was kind of helpless. Wish I could draw on here to explain what I am looking for. If I understand correctly. At or near where the case mouth sits in the charge hole there is a ramp or neck area that extends about .06" inch forward while also slightly narrowing the cylinder bore. It then is a constant diameter ( the throat ) to the end of the cylinder.. It would have a shape similar to some rifle cartridges. _______,-------- This would be just a one dimension attempt at what I am envisioning with the angle between the two lines being much less acute and the difference between the diameter of the Charge hole and the throat being much less than my crude attempt to illustrate. Moving from left to right we would have charge hole diameter, the ramp narrowing the diameter , ending at the throat which remains a constant diameter to the end of the cylinder.
I envision what you describe as a relieved bore at the breech as being what I would call the forcing cone. If I am corect in my interpretation of your post I can see in my mind what happens physically. Onlything I lack is the actual dimensions.
Now go find those pin gauges. 😉
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February 22, 2009
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For those who really need to know:
Top is the cartridge, bottom is the chamber.
Regards,
Ron
Technically, the glass is always full; half liquid, half air....
February 29, 2012
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Minus size pin gauges are really the best tool to check this.
Without pin gauges... I would use a dead soft lead slug, (or ball) and drive it through the cylinder using a brass rod then measure it.
Measure the slug using a micrometer. This will give you a general idea on the size of the cylinder throats.
In a perfect world, the cylinder throats should be somewhat larger than what the barrel slugs.
(and they almost always are)
For example:
Barrel slugs at .358
Cylinder throats slug at .360
You're good to go.
But, it looked like this this:
Barrel slugs at .358
5 Cylinder throats slug at .359
And one hole slugs at .357
I would hone them all out to .359 for consistency.
Number and check each cylinder hole to be sure that they are all the same size. If you shoot lead bullets often, as I do then you really don't want different sized cylinder throats, and you want the numbers to look like the ones above.
I'd use a reamer on the cylinder, or have a reputable smith ream the cylinder out so that they all match the largest size hole.
If you mainly shoot jacketed ammunition, doing this is not especially critical unless you have a glaring inconsistency in your measurements. In general I don't bother doing this at all, unless a revolver has a glaring problem with accuracy.
If it already shoots well, I just don't worry about it. If one cylinder hole is always throwing your groups though, then I would check it out.
- Bullwolf
December 3, 2015
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rwsem said
For those who really need to know:Top is the cartridge, bottom is the chamber.
Regards,
Ron
Yup, that would be me! Just my nature.
I have seen plenty of information on .357 cartridge dimensions. However, what this links to is Generic. I am looking for information on exactly how Dan Wesson built their cylinders. i.e. charge hole length and diameter, cylinder throat length and diameter. Is the throat diameter constant or does it taper? Length and angle of any transitional area occurring after the charge hole and before the cylinder throat.
For instance, I have read that Dan Wesson used "Taylor Throating" routinely. I do not believe this to be the case because "Taylor Throating" is employed to relieve the constriction caused at the breech end of a barrel when it is torqued to index. Fire lapping is also employed for minor constrictions. The nature of DW barrel construction and their method of installation would make "Taylor Throating" unnecessary.
I have heard talk of tapered bores. I do not believe the bore of a DW barrel is tapered. Therefore I thought perhaps this rumor if I might call it that, could be related to how the cylinders are bored. i.e. a taper from the charge hole to the muzzle end of the cylinder resulting in a continuous taperd throat.
If one is considering a modification to a stock DW cylinder to accept a 9mm cartridge some of the dimensions and physical characteristics become more important. A 9mm projectile has about a .5 inch jump to get to the forcing cone. What it encounters in that .5 inch could very well have an effect upon the overall performance of the revolver.
Guess I spent too much time building high performance engines in the past. I just have to know these things. Sort of like using a degree wheel when setting up a camshaft orindexing spark plugs.
March 22, 2016
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well, being an old dude, we used this stuff for getting exact dimensions you are asking for...
http://www.midwayusa.com/product/462291/cerrosafe-chamber-casting-alloy-1-2-lb
and it answers another issue someone is having with a stuck case broken off extraction issue... will double post it there also..
good luck
December 3, 2015
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Bullwolf said
Minus size pin gauges are really the best tool to check this.Without pin gauges... I would use a dead soft lead slug, (or ball) and drive it through the cylinder using a brass rod then measure it.
Measure the slug using a micrometer. This will give you a general idea on the size of the cylinder throats.
In a perfect world, the cylinder throats should be somewhat larger than what the barrel slugs.
(and they almost always are)For example:
Barrel slugs at .358
Cylinder throats slug at .360
You're good to go.
But, it looked like this this:
Barrel slugs at .358
5 Cylinder throats slug at .359
And one hole slugs at .357
I would hone them all out to .359 for consistency.Number and check each cylinder hole to be sure that they are all the same size. If you shoot lead bullets often, as I do then you really don't want different sized cylinder throats, and you want the numbers to look like the ones above.
I'd use a reamer on the cylinder, or have a reputable smith ream the cylinder out so that they all match the largest size hole.
If you mainly shoot jacketed ammunition, doing this is not especially critical unless you have a glaring inconsistency in your measurements. In general I don't bother doing this at all, unless a revolver has a glaring problem with accuracy.
If it already shoots well, I just don't worry about it. If one cylinder hole is always throwing your groups though, then I would check it out.
- Bullwolf
Good Info.
Rugerwas rather notorious for having undersize cylinder throats in their .45 Colt revolvers.
December 3, 2015
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rwsem said
For those who really need to know:Top is the cartridge, bottom is the chamber.
Regards,
Ron
rwsem,
My Bad! The bottom diagram just did not register with me. Bain fart I guess. If the dimensions shown there are what DW used then it is exactly what I was seeking.
As bullwolf said whether or notany one cylinder has those dimensions in every charge hole and cylinder throat can only be determined by measuring each individually. One number I have seen is a minimum.001" for the throats being over the barrel bore. A stock .357 cylinder may not be optimal for a 9mm projectile as the throats may actually be too large. This added to the large jump to the forcing cone would seem likea less than optimal situation. There are several operations that will modify a .357 cylinder for 9mm. I have held the belief that this procedure is less desirable than a dedicated 9mm cylinder. Just my opinion . Some would argue that practically there is no noticeable difference. Then of course there is the potential leading problems as well.
March 22, 2016
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man of blues said
well, being an old dude, we used this stuff for getting exact dimensions you are asking for...http://www.midwayusa.com/product/462291/cerrosafe-chamber-casting-alloy-1-2-lb
and it answers another issue someone is having with a stuck case broken off extraction issue... will double post it there also..
good luck
as I mentioned, you can make an exact casting which pops out and can be measured, have done this myself when desiring to make custom chamber reamers.. its industry standard practice.
December 3, 2015
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Different Drummer said
rwsem said
For those who really need to know:Top is the cartridge, bottom is the chamber.
Regards,
Ronrwsem,
My Bad! The bottom diagram just did not register with me. Brain fart I guess. If the dimensions shown there are what DW used then it is exactly what I was seeking.
As bullwolf said whether or not any one cylinder has those dimensions in every charge hole and cylinder throat can only be determined by measuring each individually. One number I have seen is a minimum.001" for the throats being over the barrel bore. A stock .357 cylinder may not be optimal for a 9mm projectile as the throats may actually be too large. This added to the large jump to the forcing cone would seem like a less than optimal situation. There are several operations that will modify a .357 cylinder for 9mm. I have held the belief that this procedure is less desirable than a dedicated 9mm cylinder. Just my opinion . Some would argue that practically there is no noticeable difference. Then of course there is the potential leading problems as well.
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February 22, 2009
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The only way to do that project correctly is to have a 9mm cylinder coupled with a 9mm barrel. .002 difference in diameter will make a mess when shooting lead.
Technically, the glass is always full; half liquid, half air....
December 3, 2015
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rwsem said
The only way to do that project correctly is to have a 9mm cylinder coupled with a 9mm barrel. .002 difference in diameter will make a mess when shooting lead.
I could not agree more. This is exactly what I was planning. The Pork Chop model DW or HS makes a perfect platform for such a project. Not only can the barrel be changed to one of a proper bore and twist rate but a complete cylinder assembly could be swapped out very easily while the barrel is removed. A cylinder that is designed for a 9mm cartridge that head spaces off the case mouth with properly sized throats is the way to go. About a year ago I discovered that Dan Wesson in Norwich had about a dozen of these cylinders sitting on shelves collecting dust. I have no idea why they had them or what they were originally designed for. All have since been sold. However, there is one available that I can purchase. If I cannot do it correctly I will not do it at all. Right now I am starting to think that it is not a cost effective adventure compared to buying a production 9mm revolver. If the Korth Sky Marshall can find it's way to our shores I believe that would be the way to go. It is a purpose built 9mm revolver from design concept to finished product.
As I stated in another thread the sometimes maligned Taurus manufacturing is one company that appears to attemt to do it correctly. The Taurus M905 has chambers cut for 9mm. Cartridges headspace off the case mouth. ( Revolver can be fired without moon clips, they are mostly for ease of extraction and ease of loading). Barrel is of proper dimensions and twist rate is 1:9.5. I cannot say what the cylinder throats measure. However, if they went to the trouble to get other parameters correct I am guessing the cylinder throats are of proper size.
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