The "Open Top" platform.

45 Dragoon said:
You guys are right as far as being conversions . . . and you can't tell by looking but these revolvers shoot ( currently) lower end "Ruger only" loads. Just thought some folks might like seeing some "REAL" revolvers lol!!!

C'mon man, you can't shoot hot loads in an open top, they will self destruct on the first round.
(You knew someone was going to say it)
Seriously though, an open top cartridge gun would be a very welcome addition to my SA accumulation.
I'd like to find one in 38 Spl.
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armoredman said:
Open top conversions, while awesome, are usually limited to "cowboy" loads for safety.
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That is correct. It's really more about the "build" and tolerances of the platform than the cylinders. I'm just showing what the platform CAN support when done correctly. The cylinders are Kirst and the revolvers are Uberti. I haven't done any testing with Pietta.

Mike
 
While those are open top revolvers, they are not truly "Open Tops", but rather cartridge conversions. Minute point I know, but Open Top nomenclature is used to describe revolvers originally produced from a the factore as cartridge revolvers, as opposed to those made as cap-and-ball guns then converted to accept cartridges. The add-on breech ring is the defining point. Open Top frames were produced originally as cartridge guns. And the Colt Open Top was .44 Rimfire while the Colt conversion was .44 Colt centerfire.

Here is a Cimarron Open Top Navy, a replica of a non-existant revolver. The Open Tops have the rear sight (If you can call it that) on the breech end of the barre. Most conversions have the rear sight on the breech ring, though some still kept the notch in the hammer.

100_9990_zpsa6qjrqvc.jpg

I know, picky,picky, picky!

Bob Wright
 
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Well, the "platform" across the board is "Open top" as opposed to "Top Strap". I should have included "platform " in my post like I did in the title.
I use open-top rather than 1860 Army or '51 Navy or Dragoons or Walkers if I'm taking about multiple models.

All in all, no harm no foul . . .

Mike
 
Not really concerned about the strength of the cylinder, but I've always been suspicious of the strength of a gun held together strictly by the cylinder arbor.
Please, no disrespect, but who is making the judgement that these (really elegant) revos are strong enough for any kind of "Ruger only" load?
Gotta admit an open top of any sort, in .45 Colt, would be cool. Mine have always been in .38Spl, and I've kept loads in the full charge wadcutter range. (These are loaded to the same level as the old 158 gr RNL.)
Moon
 
halfmoonclip said:
Not really concerned about the strength of the cylinder, but I've always been suspicious of the strength of a gun held together strictly by the cylinder arbor.
Please, no disrespect, but who is making the judgement that these (really elegant) revos are strong enough for any kind of "Ruger only" load?
Gotta admit an open top of any sort, in .45 Colt, would be cool. Mine have always been in .38Spl, and I've kept loads in the full charge wadcutter range. (These are loaded to the same level as the old 158 gr RNL.)
Moon
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Well, I reckon I am . . . that's kinda what I meant by the "build and tolerances" when they are set up to be converted. You shouldn't shoot anything in a "rattle trap ". I'm using mine for "platform testing" to do exactly that . . . see what the platform can take. I'm not even advocating anybody do what I'm doing I'm just letting you know just how good that platform IS. Mind you, I'm definitely not wanting to destroy my revolvers, but I'm confident in what they can handle and will stop at the first sign of any structural change. Heck!!! They're too pretty to just mess um up on purpose!!

Mike
 
As to the importance of that top strap, I'll share my experience:

I hae a Colt SAA .357 Magnum that has been customized, including milling out the top strap for a S&W rear sight. I was shooting some 140 gr. JHP magnum loads one day when my groups started climbing unexpectedly. After a few more groups each climbing higher, the cylinder was difficult to turn. Examining my Colt, I saw the rear of the cylinder was binding against the top strap. Looking more closely, the barrel was angled noticibly downward. That top strap has stretched so tha the barrel was way out of line.

I thought I had reduced that Colt to a parts gun, but my gunsmith did realign the frame for me, and advised me to keep it within .38 Special vicinity ammunition.

As for the ammunition, my handlords were made up around the 140 JHP Speer (I believe) at around 1500~1550 f.p.s. range using Winchester 296 powder. So not a really hot nor heavy load.

Bob Wright
 
Lots of folks don't realize that the arbor in an open-top platform IS the top strap. It serves the same structural purpose of a top strap in the top strap design. Because of the design layout of the open-top, it handles the forces generated from firing rather well . . . It makes for a much more compact structure than the more spread out "top strap " design which is part of why it is an excellent platform. The problem with it is in the "build" and setup. The design comes from the mechanical age when function was king and form followed.
The original 1860 Armys I've had the pleasure to work on, take copious pictures of, and actually do a full Outlaw Mule service to one ( posted about here) are all a testament to DESIGN!!! They will still function today as intended !! But, the materials our "reproductions" are made from is vastly superior to the originals!! They should last FOREVER but the vast majority wont!! Because they weren't built as designed. Of course, that can be corrected and that's why these revolvers can handle these type loads . . .
I here ya Bob Wright, I've had a like "top strap" failure. I'll keep testing and reporting on these "modern but corrected" open-top platform revolvers.

Mike
 
45 Dragoon said:
Lots of folks don't realize that the arbor in an open-top platform IS the top strap. It serves the same structural purpose of a top strap in the top strap design. Because of the design layout of the open-top, it handles the forces generated from firing rather well . . . It makes for a much more compact structure than the more spread out "top strap " design which is part of why it is an excellent platform. The problem with it is in the "build" and setup. The design comes from the mechanical age when function was king and form followed.
The original 1860 Armys I've had the pleasure to work on, take copious pictures of, and actually do a full Outlaw Mule service to one ( posted about here) are all a testament to DESIGN!!! They will still function today as intended !! But, the materials our "reproductions" are made from is vastly superior to the originals!! They should last FOREVER but the vast majority wont!! Because they weren't built as designed. Of course, that can be corrected and that's why these revolvers can handle these type loads . . .
I here ya Bob Wright, I've had a like "top strap" failure. I'll keep testing and reporting on these "modern but corrected" open-top platform revolvers.

Mike
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I will agree that the cylinder arbor is sort of/kiknd of the top strap and it is beefed up in design to take the forces, but the location makes the difference. The real top strap is further from the rotation and has more length of leverage for a stronger hold, sort of the same principle of a deeper steel beam versus a smaller one.

Bob Wright
 
BobWright said:
I will agree that the cylinder arbor is sort of/kiknd of the top strap and it is beefed up in design to take the forces, but the location makes the difference. The real top strap is further from the rotation and has more length of leverage for a stronger hold, sort of the same principle of a deeper steel beam versus a smaller one.

Bob Wright
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Well, the arbor is a stressed member so it really "has to be" the "upper most" member of the platform (whether a cylinder rotates on it is beside the point). . . It's definitely not a "base pin" which isn't a stressed frame member.
Ask an engineer and they will tell you the 4 sided structure is the weakest structure to contain an uneven force (( the bigger the weaker) the reason our top straps turned into trapezoids). The open-top structure is a more compact version of the same configuration which translates to stronger. The only way to gain strength in a top strap is a thicker/ wider top strap or exotic materias( i.e. FA, BFR's, . . . ).

To wit, a cylinder I know the parameters of which allows me to in fact "test" the foundation of ( platform) which thus far has absolutely been 100% no problem at all with 23K psi ammo. I realize "more testing" is needed ( I'm only at the 1,000 round mark but I'm a busy guy !!) but so far, these revolvers are a far step from my bent ( from bp no less) top strap - and, this is 4 revolvers, not just one . . .
So, I'll keep testing and reporting . . .

Mike
 
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Cocked & Locked said:
View attachment 1156743 Just one. .38 Colt / .38 Special Uberti Cimarron
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That is like the "Open Top Navy" I had, and likely might be the photo that prompted me to buy min in the first place. Beutiful gun, well made and fitted, but I just couldn't wrk with those impossible sights! Ond I had a hard time sighting in the gun, filed the front sight down almost to a nub! And, I thought it was surprsingly heavy for its size. This due to the barrel assembly.

100_0018_zpsmunuvo5f.jpg

100_9981_zpskm7psd7p.jpg

Bob Wright
 
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I like the looks of the Open Top with Navy grip, even if not strictly authentic.
I would get it in .44 or .45 for balance, a .38 hole in C&B or SAA barrel and cylinder just makes for a heavy awkward gun in my hand.
If I were shooting SAs more these days I would take the unused rammer off my Legal Defender, which is a really queer duck conversion.
 
.45 Dragoon, enjoy your experiments, though it all has an Elmer Keith feel (up the load 'till you blow it up, and then back off by 10%...) Personally, I'll keep my WFO loads in a Smith .44. With a top strap.... ;)
I do feel a little better shooting those Full Charge wadcutters, I was feeling kind of guilty about that.
Yeah, the sighs on an Open Top are a challenge, even for someone with younger eyes than me. Remind yourself, these guns weren't headed to Camp Perry, they were simply supposed to shoot minute of human. What works for me; bring the front sight up out of the notch on the barrel.
Moon
 
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