I'm sure you are all aware of the differences between the standard model 3 and the Schofield.
Howdy
There was no such thing as a "standard model 3".
There were five separate and distinct Top Break revolver models that Smith and Wesson built on the #3 sized frame.
Here are some photos illustrating the differences.
The American Model was the first Top Break revolver that S&W produced. The Rollin White patent, which S&W controlled, was due to expire in 1869. This patent gave S&W the exclusive right to manufacture revolvers with chambers bored through to accept cartridges. Daniel Wesson was sure the other revolver manufacturers would have their own versions of cartridge revolvers ready to sell once the patent expired. So his engineers came up with a totally new concept, a revolver that broke open by rotating the barrel down, and automatically ejected spent brass. The American model was first manufactured in 1870, and the US Army bought 1000 of them, the first revolvers designed to shoot cartridges that the Army bought. The American Model fired a 44 caliber cartridge that used a heeled bullet, meaning the rear of the bullet was of the same diameter as the inside of the cartridge case. The round was known as the 44 S&W American cartridge. This is not actually an American model, it is a 1st Model Russian. Outwardly exactly the same as the American model, except chambered for the 44 Russian round. Interestingly enough, Colt did not manufacture the Single Action Army until 1873, three years after S&W introduced the American Model.
This is a Russian model. Specifically it is a 2nd Model Russian. Notice the distinctive hump on the grip and the spur on the trigger guard. After buying a bunch of 1st Model Russians the Russians specified some changes, which included the grip shape and the spur on the trigger guard. The grip shape was intended to prevent the grip from rotating in the hand due to recoil. It did a very good job of this. Unfortunately, I find this model very awkward to shoot. The shape of the hammer spur on all S&W #3 Top Breaks means there is a long reach to the hammer spur when cocking the hammer one handed. They are all like that. However I find that I cannot reach the hammer spur with my thumb unless I shift my grip and place the palm of my hand directly on that pointy hump (S&W calls it a knuckle). Then I have to regrip again to get my hand below the hump. If I forget and fire the revolver with the hump in contact with my palm, it hurts, even with a mild recoiling round such as the 44 Russian. For that reason I never recommend this model to prospective buyers of S&W #3 Top Breaks.
The Russians also dictated the new round for this revolver, the 44 Russian round, would not use a heeled bullet, but instead would have the bullet lube in grooves on the bullet. The bullet was the same diameter as the inside of the case, so the bullet lube would remain inside the cartridge case and not attract contamination like rounds with heeled bullets tended to. Which by the way, is why the 44 Russian, 44 Special, and 44 Magnum cartridges all use bullets that are .429 in diameter.
About the spur on the trigger guard, I have heard many explanations. I believe the Russians simply wanted it because it is a 19th Century European style affectation. No, it is not a good place to rest the middle finger when shooting, I have tried.
This is the Schofield Model. Distinctive because of George Schofield's patented latch system. He developed this style latch working with a Gunsmith on an American model. The serpentine latch was mounted to the frame, as opposed to the latch on the top strap of the two previous models. Schofield designed it so a mounted trooper could unlatch the barrel with one hand, while riding, brush the barrel against his leg to rotate the barrel down and eject the empties, and reload, all while riding at a full gallop. I am not a horseman, but I can reload a Schofield the same way while sitting in a chair. When S&W approached the Army about a contract with the government, the only cartridge the Army was using was the 45 Colt. S&W would have no problem opening the bore up from 44 to 45 for the new revolver, but a 45 Colt cartridge was too long to fit into the 1 7/16" long cylinder S&W was using with all their Top Breaks. Rather than retool and interrupt the flow of the over 150,000 Russian models they eventually built, S&W got the Army to compromise on a new cartridge that would fit into the 1 7/16" long cylinder. Thus was born the 45 Schofield cartridge. S&W had to pay Schofield a royalty of fifty cents for every revolver they made using his patented latch. Daniel Wesson instructed his engineers to come up with a similar latch that would circumvent Schofield's patent. Only about 9,000 Schofields were ever made in two models, from 1875 until 1877 and Wesson's engineers never came up with an alternative latch.
This is the New Model Number Three. In my humble opinion this model was the best of all the #3 Top Breaks S&W made. Introduced in 1878 and eventually chambered for 17 different cartridges, although 44 Russian was the most common. A shorter, rack operated ejector rod meant a shorter ejector rod housing under the barrel. A simpler system to remove the cylinder than any of the previous models. And a rebounding hammer, although personally I would never trust it and only ever load mine with five rounds with an empty chamber under the hammer. A new grip shape very similar to a modern K frame S&W revolver with a very small knuckle on the grip. I always recommend to anyone interested that this is the best of the S&W #3 Top Breaks.
Finally, the 44 Double Action. This was the only double action revolver S&W built on the large #3 sized frame. This one is a target model with a windage adjustable rear sight and a target front sight with a bead on top. Most commonly chambered for 44 Russian, but about 15,000 were chambered for 44-40, and 276 were chambered for 38-40
To answer some of your questions:
Yes, all modern replicas of S&W #3 Top Break revolvers are made by Uberti. Many years ago ASM was building a replica of the Schofield model, but they were very poor quality.
Here is why the modern replicas made by Uberti generally do not do well when shot with ammunition loaded with Black Powder.
As I stated earlier, almost all of the originals were made with cylinders 1 7/16" long. (Those that chambered 44-40 or 38-40 had longer cylinders).
When Uberti and ASM made their first replicas, they made the cylinders longer to accept longer cartridges such as 44-40 and 45 Colt. But they did not lengthen the frames a similar amount. This meant the bushing on the front of the cylinder had to be shortened to fit into a same sized frame. See my recent post about the Schofield Model of 2000 so I don't have to post all the photos again. Anyway, with the shortened bushing on the front of the cylinder, Black Powder fouling blasted out of the barrel/cylinder gap on these replicas tends to make them bind up more quickly than the originals when fired with ammunition loaded with Black Powder. Not impossible, plenty of Black Powder compatible bullet lube on the bullets as well as frequent wiping down makes them perform reasonably well with ammo loaded with Black Powder. Check out Big Lube bullets.
http://www.whyteleatherworks.com/BigLube.html44 Russian and 44-40 are very different. Besides being longer, 44-40 has a tapered case. 44 Russian, 44 Special, and 44 Magnum all have the 44 Russian as their ancestor. Any revolver chambered for 44 Special can also fire 44 Russian. Any revolver chambered for 44 Mag can also fire 44 Special and 44 Russian. Any revolver chambered for 44 Russian can only chamber 44 Russian ammunition.
44 Russian ammunition was quite common in the US.
I load 44 Russian with Black Powder all the time. I use the same Big Lube bullets that I use with 44-40. I buy the 44 Mav-Dutchman bullet from Whyte Leather and have them sized to .428, rather than the normal .427 because I have 44-40 rifles that have a couple of different groove diameters.
I know the idea of the Schofield latch was to do it one handed, but the regular 'press up' latch of the model three seems like it would be just as easy to do one handed, and you'd need both once you are putting the rounds in anyway, right?
No. In my experience it is much easier to open the Schofield style latch one handed than the style of latch on all the other #3 Top Breaks. Doing it right now on a NM#3. Right hand gripping the grip, right thumb shoves the latch up. Left hand grabs the barrel and rotates it down. The ergonomics of the Schofield latch make it easier to pull back with the thumb of the hand holding the revolver. That's why old Daniel Wesson wanted his engineers to find a way around Schofield's patent but still retaining the general idea.
I think somewhere in there you asked about the strength of the two different styles of latch systems. They were completely adequate for the ammunition they were designed for. In addition, all firearms made in Italy are proofed in government proof houses. Any modern Italian replica will be completely safe to shoot with modern Smokeless ammunition that adheres to SAAMI industry pressure stancards.
Personally, I never shoot my antique Top Breaks with anything other than ammunition I load with Black Powder. Yes, it is the pressure spike. The older steel cannot always take the rapid pressure spike generated by most Smokeless powders.
Yes, cleaning up after shooting Black Powder is messy, much messier than cleaning up after shooting Smokeless. However I have found over many years that cleaning up after shooting BP actually takes less elbow grease than cleaning up after Smokeless, and BP solvents are water based, rather than nasty smelling Smokeless solvents.
And Black Powder is not as corrosive as most shooters think. After a match I am usually too tired to sit down and clean two pistols, a rifle and a shotgun. I try to clean them within a week. I am not going to state in public how long I have actually let them sit without cleaning, suffice it to say it has been much longer than a week. And they have not corroded into piles of rust.