Howdy
A few thoughts.
In February of 1868 Remington signed a contract with Smith and Wesson to convert 4,574 44 caliber Cap & Ball revolvers (the New Model Army, often known as the 1858 Remington because of the patent date) to cartridges. The backstory is that S&W still controlled the rights to the Rollin White patent for bored through cylinders for cartridges, so S&W had to agree in order for the work to be done. The contract stipulated Remington would do the work, and S&W would inspect the final products. S&W charged $1.00 per revolver as their fee for allowing Remington to do the conversions. Most of these revolvers were converted from six shot C&B cylinders to five shot 46 Rimfire cartridges.
Here is a photo of one.
Individual gunsmiths had been doing conversions of Remington C&B revolvers for some time, and because they were very small operations, S&W was not able to track them down for patent infringement.
Here is a photo of a Remington converted for cartridges by an independent gunsmith.
Looks good but I'll never understand the urge to go out and buy a percussion revolver only to slap a conversion cylinder in it, of a design not in use during the old west. It's not historically accurate and its not interesting. There are replicas of the Remington 1875 available, did you know that?
A valid point. In my own case I had bought my EuroArms Remington so long ago (1975) that when I decided to buy a cartridge conversion cylinder for it about ten years ago it was like I was getting a new cartridge revolver for $150 or so, if I remember correctly what I paid for the cylinder.
A few months later I came across a used Stainless Uberti Remington that came with a 45 Colt conversion cylinder for about the price of a new cartridge revolver. So it was a no brainer that I would grab that Remmie too. (Need two pistols to compete in CAS.)
Here is my brace of cartridge conversion Remmies. Yup, the stainless Uberti came with a blued conversion cylinder. I have no problem with that.
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Regarding the strength of cylinders and frames: It is not the frame that must withstand the pressure spike of a cartridge firing, it is the cylinder. True, many times you will see the top strap blown off a frame when the cylinder fails, but that is because pieces of the cylinder took the top strap with it. It is also true that sometimes a frame will stretch, or might even crack, but that is not from the pressure of a cartridge firing. That is from the concussion of many high powered rounds being fired and battering the frame. But generally speaking, it is the cylinder, not the frame, that is the pressure vessel in a revolver. If you don't blow up the cylinder, you most likely will not blow up the gun. As a caveat I will add that all the conversion cylinder manufacturers stress that their conversion cylinders should only be used in steel framed C&B revolvers, not revolvers with brass frames. With a brass frame one might well exceed the tensile strength of the brass, and the frame might stretch.
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Here is a photo of my old EuroArms Remmie with its Taylors six shot 45 Colt conversion cylinder.
A few comments. You will notice the cylinder cap does have the slots between firing pins to drop the hammer nose into so the cylinder can be loaded with six shots. Unfortunately, the slots are not wide enough, the nose of the hammer will not drop into them. Yes, I could have shaved down the hammer nose a little bit, but I only ever load a single action revolver with five shots anyway. You will notice that one of the firing pins is silver colored, rather than blued. That is so the shooter can keep track of which chamber is empty.
Yes, this is one of the original cylinders that Ken Howell made under contract for Taylors. Yes, the chambers do splay out less than 1/2 of one degree at the rear in order for the 45 Colt rims to not interfere with each other. That is the only way six 45 Colt chambers could be bored into a cylinder that will fit into a replica 1858 Remington without the rims bumping into each other. No, the slight angle does not affect accuracy at all, my conversion cylinder Remmies are the most accurate 45 Colt revolvers I own, more accurate than my Colts, Rugers, or Ubertis. I believe the precision of the dimensions of the chambers is the reason for that. The chambers on these cylinders are tighter than the chambers in any of my other 45 Colt revolvers. In fact, when reloading 45 Colt I always use one of these cylinders as a 'cartridge gauge'. If a crimped round will drop into the chambers of one of these cylinders, I know it will also drop into the chambers of my other 45 Colt revolvers.
Yes, when Ken Howell sold his patent for the angled chambers to Taylors, he was no longer able to make the six shot cylinders for the 45 Colt Remington. Taylors is currently contracting with someone else to make them.
I did not know the cylinder cap was cast, that is new information for me and I thank Drobs for that information. Yes, the cylinder cap does have a slightly 'pebbly' finish. I never thought about it too much, but that could well be indicative of a sand cast part. I should have realized the cap was sand cast because there are no telltale radii in the slots that would have been left behind if the slots had been milled.
Another interesting feature of my cylinders are the 'viewing windows' cut into the sides of the cylinder. They did not exist when I bought the cylinders. As purchased, the counterbores for the cartridge rims would accept 45 Colt rims, but they would not accept the slightly larger diameter (.520 vs .512) of Schofield rims. So I had a gunsmith friend open up the diameter of the counterbores to accept the Schofield rims. Before he opened up the counterbores, we realized there would be a paper thin amount of steel remaining between the larger counterbores and the outside diameter of the cylinder. So we decided to cut straight accross, eliminating the paper thin sliver of steel and thus creating convenient 'viewing windows, which help indicate where the empty chamber is. With the cap on, you can't tell unless you look down the barrel. I understand the cylinders Taylors is selling now also include the 'viewing windows', and I believe they will accept 45 Schofield rims. Perhaps they discovered what we discovered,
All of this gets me to my last point, regarding the strength of the 1858 Remington frame. I don't think the frame is particularly strong. The hole drilled in the frame where the loading ram pokes through makes the cross section of the frame pretty thin there. I think if the frame were to fail anywhere form repeated concussion, that is where it would crack. Right where the ram pokes through. Also, I discovered that unlike the 1873 Colt, the grip shape of the 1858 Remington is just different enough that full power loads are a little bit uncomfortable to shoot. I shoot 45 Colt Black Powder loads stuffed to the gills with FFg and a 250 grain bullet through my Colts all the time. But the grip shape of the Remington makes my hand smart a bit with those loads. That is why I usually shoot 45 Schofield ammo in my Remingtons. The Schofield case holds significantly less FFg than the 45 Colt round does, and I cap them with 200 grain bullets, rather than 250, which produces milder recoil which is friendlier to my old hands than full house 45 Colt BP loads.
Finally, regarding shooting more powerful Smokeless loads through a conversion cylinder:
I would not do it. My cylinders came with a specific disclaimer stating to only shoot them with Smokeless 'Cowboy' loads. Unfortunately, there is no SAAMI standard for what makes a 'Cowboy' load. And forget about trying to define loads by velocity. Velocity is not what blows up cylinders, pressure is what blows up cylinders. One can achieve X feet per second by various combinations of bullet weight and various charges of various Smokeless powder. But the actual pressure can vary widely. Without using sophisticated pressure equipment, the average reloader really has no idea how much pressure his loads are creating.
I am reasonably sure that these cylinders have been proofed for SAAMI Spec 45 Colt loads. 14,000 psi if I recall correctly. I would not push them beyond that.