Colt uses different designations for their revolver frames. Rather than making a list, let me provide this link for your review -- it is more complete than what I could provide myself with regard to the newer Colt revolvers:
http://www.thefiringline.com/forums/arc ... 37598.html
For my own comments, may I say that the old Colt frames, the D, E/I, and New Service, tended to be a bit larger than the S&W counterparts.
For instance, the D frame Colt in .38 Spl holds 6 rounds, while the J frame S&W holds 5. The Detective Special is a somewhat larger weapon than a Chief's Special, for instance. As you may note from the linked list, these were originally intended to be .32 caliber revolvers. When they were adapted to use .38 cartridges, the S&W J frame could only hold 5 cartridges, but the D frame Colt could manage 6. However, Colt had to lengthen the cylinders when the longer .38 Special round was introduced, reflected by changing the name of the weapon from "Police Positive" to "Police Positive Special".
Regarding the S&W K and L frame compared to the E/I Colt frame, the .41 designation should tell you something. Colt chambered their "Army Special" (first of this frame family) for .41 Colt, besides .38. Years back, most revolver bullets were "heeled" bullets that were outside lubricated. The various .22 RF are about the only common modern ammunition that uses this style today. The upshot to this is that the bullet is the same diameter as the
outside of the case.
Outside lubricated bullets in the old days were messy, as the lubricant collected dirt and deteriorated. The use of inside lubricated bullets ended that problem, but the bullet diameter is reduced from being the same diameter as the outside of the cartridge case to being the same diameter as the inside of the case.
So, .38 caliber rounds began using .354-.357 sized bullets of the inside lubricated design and .44 caliber rounds began using .429 sized bullets.
For Colt, this meant that the .41 Colt began using .387 sized bullets, reduced from .401. But Colt did not reduce the bore size of the gun. Instead, they used hollow based bullets that upset on firing to fill the bore, like the old musket Minie Ball.
This meant that Colt revolvers in the medium frame size were actually made for .41 caliber ammo, where the S&W K frame was intended for .38. After .357 Magnum was introduced, the larger Colt I frame Python was able to handle the new round without a change in size, but the Model 19 K frame S&W was somewhat more stressed by the more powerful round. S&W's answer was to increase the K frame slightly, which they then called the L frame.
The Colt New Service was more nearly the same size as the S&W N frame (used for the .44 Magnum), however you will note that the grip of the Colt New Service is further behind the trigger guard than it is in the S&W N frame. This makes the New Service frame revolvers somewhat more manageable for those of us with large hands.