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Old February 22, 2011, 05:42 PM   #1
Rachen
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BP Revolver pressure (PSI) and conversion cylinders

What pressures are steel frame reproductions typically rated for? Specifically 1858 Piettas?

Also, Kirst converters require you to machine a channel in the gun's recoil shield. Does this affect the structural integrity of the frame?
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Old February 22, 2011, 06:05 PM   #2
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Nobody really knows the answer to that. There was a letter floating around a while back that Pedersoli supposedly sent to those who asked about their BP cartridge rifles. They said that the rifles were tested with a charge 30% greater than normal. But as far as a C&B revolver, it's pretty much a mystery, at least to the best of my knowledge.

We know that you can put as much powder in an 1858 as it will hold and nothing untoward will happen. And based on R&D and Kirst's testing, we know that "cowboy" loads will be just fine in a steel framed revolver. And, as far as I know, that's the sum of the public knowledge of what a C&B revolver will do.

Incidentally, whatever testing the Italians do would be based on the European standard (I forget what it's called) and wouldn't really translate into a SAMMI-compatible value. Again, that's just my understanding - I've never found anything like a conversion table between any of the proofing standards.

Cutting a channel in the recoil shield will not affect the strength of the revolver - it's a non stress bearing part of the frame.
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Old February 23, 2011, 05:46 AM   #3
kadima
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Testing of arms at Gardone Val Trompia proof house is done according to CIP specifications.

Some informations can be had at the proof house itself (they answer in English)
http://www.bancoprova.it/index.php/it/home.html

or at the CIP http://www.cip-bp.org/

Hope this helps

K.
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Old February 23, 2011, 09:21 AM   #4
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Quote:
Cutting a channel in the recoil shield will not affect the strength of the revolver - it's a non stress bearing part of the frame.
The recoil shield is stress bearing. When fired as a cap and ball the cylinder is pushed back into the recoil shield centered on the arbor/cylinder pin. When fired as a cartridge revolver this recoil is at top of the recoil shield. This may cause cracks in the open top Colts at the bottom of the frame at the bolt pivot screw.
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Old February 23, 2011, 10:04 AM   #5
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Velocity limitations..not psi

The original Konverter data was simply.."Keep loads at "Standard" pressures and 1000fps or less., We have now added the word "Cowboy" ... but this Cowboy recomendation has no PSI limit..just a Velocity limitation..

While cowboy loads are Low velocity, many of them use VERY FAST powders, which generate LOTS of pressure. TiteGroup for example..opperates at the full alowed SAMMI pressure of standard 45colts, but the velocity is still at 800fps or a little less with a 255gr.

You can take this same pressure, with a slower powder and get much more velocity.. Like black powder for instance..or even Unique or BluDot etc.

Then there is the 45ACP cylinders.. this thing runs at 21,000 PSI!!! but still doesn't get past 1000fps. This is still allowed in the conversion cylinder

So I think that frame stretching inertia/velocity from the bullet was more of a concern for the conversion cylinder Co.'s than Pressure.

I just got a 5 round Kirst Saftey Cylinder with NO loading gate.. so there is NO need to alter my revolvers recoil shield in any way. I had an R&D, but I think that this 5 round Kirst cylinder is the way to go.
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Old February 23, 2011, 10:21 AM   #6
Hardcase
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Quote:
The recoil shield is stress bearing. When fired as a cap and ball the cylinder is pushed back into the recoil shield centered on the arbor/cylinder pin. When fired as a cartridge revolver this recoil is at top of the recoil shield. This may cause cracks in the open top Colts at the bottom of the frame at the bolt pivot screw.
You're right - what I was trying to say was that the particular area where the channel was cut was not stress bearing because there's no metal there to bear stress - the capping channel is already cut. I just didn't do a very good job of saying it.

Now that I think about it, though, there is probably some stress transferred through the back of that area, but cutting the channel isn't going to appreciably weaken the frame.
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Old February 23, 2011, 11:02 AM   #7
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Quote:
cutting the channel isn't going to appreciably weaken the frame.
+1

I haven't heard about much of a problem with frame cracking on clone Colts, possible better steel than the originals. The Uberti Manson conversions have a better frame heat treatment from Uberti so it is something they considered.
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Old February 23, 2011, 12:28 PM   #8
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I have a kirst in my 58 the kirst has the gate but i chose not to port the frame its kinda nice you can still open the gate to check for unfired rounds. I just herd last week that someone blew up a R&D six shot they were useing hand loads so it could have been a over load. the kirst is a better conversion if you ask me. with the bullet passing straight through the forcing cone causes less strain on the frame IMO.
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Old February 23, 2011, 01:58 PM   #9
ClemBert
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Quote:
Originally Posted by Rachen
BP Revolver pressure (PSI) and conversion cylinders

What pressures are steel frame reproductions typically rated for? Specifically 1858 Piettas?

Also, Kirst converters require you to machine a channel in the gun's recoil shield. Does this affect the structural integrity of the frame?
From what I recall the reproduction revolvers aren't "RATED" up to a specific pressure. You can stuff all the BP you can cram into the cylinders leaving room for your projectile (making sure there isn't an air gap) and these revolvers will handle it. With regard to conversion cylinders they are all specified as being able to handle any "cowboy load" (less than 1000 ft/sec). With BP cartridge loading this typically means that you can stuff the brass with as much as you can cram in and not have to worry about exceeding 1000 ft/sec. YMMV!

You do not "need to" cut a channel for any of the conversion cylinders. In fact, you can buy a conversion cylinder that has no loading gate at all. Therefore, the channel wouldn't do you any good on those conversion cylinders. However, if you buy one with a loading gate it is more convenient to have that channel cut out.

Quote:
Originally Posted by kameron454ci
I have a kirst in my 58 the kirst has the gate but i chose not to port the frame its kinda nice you can still open the gate to check for unfired rounds. I just herd last week that someone blew up a R&D six shot they were useing hand loads so it could have been a over load. the kirst is a better conversion if you ask me. with the bullet passing straight through the forcing cone causes less strain on the frame IMO.
The person you are referring to was specifically using smokeless powder NOT black powder. It was probably a double charge. The OP was not clear on whether or not he'd be using smokeless loads or BP loads.

Regarding the R&D design (which has no loading gate) I haven't seen or heard of any evidence that states or implies that the 6 shot cylinder with angled cylinders has any issue with regard to accuracy nor frame strain.

IMHO, I'd channel out the frame and go with a gated Kirst cylinder for this specific revolver. I'd shoot BP loaded cartridges just like these revolvers were designed for. Its a heck of a lot more fun than a fella should have with his pants on.
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