Howdy
You said 'School me on S&W 357 revolvers', right?
S&W began producing a modern double action revolver for the brand new 38 Special cartridge in 1899. They looked like this. This is a S&W Model of 1899, that left the factory in 1899.
The cylinder for this model was the perfect size for the then new 38 Special Cartridge. Not too big, not too small, just right. And the frame was just the right size to house the cylinder without being too big or too small.This frame size became known as the K frame.
As the new century wore on, S&W began development of a new, more powerful loading for the 38 Special cartridge. This cartridge was too powerful for the K frame 38 Specials of the day. Given the steel being used at the time, the dimensions of the cylinder were not stout enough to take the pressure developed by the more powerful cartridge, sometimes known as the 38 Super Police.
In 1908 S&W had introduced a larger revolver, for the then new 44 Special cartridge. Because the 44 caliber cartridge was larger in diameter than the 38 caliber cartridge, the cylinder had to be scaled up to accept the new cartridge. The frame had to be larger to accept the larger cylinder. This new frame size became known as the N frame. It was a fairly simple task to chamber the larger cylinders to accept the 38 Special cartridge. When the larger cylinders were chambered for the smaller diameter cartridge, there was more metal left between chambers than with the K frame 38s, so these cylinders would be able to accept the higher pressures generated by the more powerful 38 Special cartridges. So in 1930 S&W introduced two 38 Special revolvers built on the larger N frame. There were two versions, one with adjustable sights and one with fixed sights. Because these revolvers were built on the N frame, originally developed for 44 Special cartridges, the fixed sight version was called the 38/44 Heavy Duty and the adjustable sight version was called the 38/44 Outdoorsman.
This is an N frame 38/44 Outdoorsman.
The tale continues. The problem was that a K frame 38 Special revolver could accept the 38 Super Police cartridge into its chambers, with possibly disastrous results. So in 1935 S&W introduced a new high powered replacement for the 38 Super Police cartridge. The cartridge case for this round was about 1/10 inch longer than a 38 Special, so the new round would not fit into a standard 38 Special revolver. The new round was dubbed the 357 Magnum. Bullet diameter was the same as the 38 Special (.357). A new revolver, very similar to the 38/44 guns was built on the N frame. This revolver was simply called The 357 Magnum. Early on these new 357 Magnum revolvers were part of a marketing program where the buyer had many choices of features on the revolver, including barrel length, type of sights, grips, and other stuff that I can't remember right now. These revolvers were called the Registered Magnums because the factory registered them to a specific owner. Sorry, I do not have a photo of a Registered Magnum, it is still on my bucket list.
The N frame 357 Magnums were big heavy guns. Bill Jordan, along with several other respected shooters, suggested to S&W that they chamber the 357 Magnum cartridge into a lighter revolver, specifically a K frame revolver. Betting that the material strength of their cylinders had improved enough, in 1955 S&W introduced the 357 Combat Magnum, built on the K frame.
In 1955, S&W changed over to a Model Number system to market their revolvers. The N frame 357 Magnum became the Model 27, and the K frame 357 Combat Magnum became the Model 19. Here is a Model 19-3 that I bought in 1975.
Here is a Model 27 that left the factory in 1959.
Here is a comparison of the sizes of the Model 27 at the top, and the Model 19 at the bottom. Don't be confused by the appearance of the large Oversized Target grips on the Model 19. The N frame Model 27 is a larger gun and has a larger cylinder.
Here is a comparison of the two cylinders. Both are chambered for the 357 Magnum cartridge. Notice how much larger the Model 27 cylinder on the right is, and how much more metal there is between chambers. That cylinder configuration goes all the way back to the 38/44 revolvers of the 1930s.
The problem with the K frame 357 Magnums, such as the Model 19 was that there was a flat relief cut onto the bottom of the forcing cone. This feature goes back to about 1905 or so with all K frame S&W revolvers. The relief was there to clear the gas collar on the cylinder. This meant that the forcing cone was slightly thinner in this area. This is a photo of the clearance cut on the bottom of the forcing cone of a Model 13-2, another 357 Magnum revolver built on the K frame. This was never a problem with normal velocity 38 Special ammunition, but with some high velocity 357 Magnum ammunition the forcing cone could split at this thin spot.
This design flaw did not exist on the N frame revolvers because the cylinder was a larger diameter. This is the forcing cone of an N frame Model 28 357 Magnum revolver. Notice there is no flat cut onto the forcing cone, it is the same thickness through out its diameter.
This is the reason S&W developed the L frame. Slightly larger than a K frame, not as large as an N frame. This is the forcing cone on a 357 Magnum S&W Model 686. No weak spot milled into it.
That's about all I can 'school you' about S&W 357 Magnum revolvers.
There are J frame 357 Magnums, but I don't own one. Much too much recoil in a small package for me.