Yes, the cylinder window is the same on all N frames and the cylinders are all the same diameter. The 357, 44 special, as well as the 25-3 and earlier 45 colts are all about 1/8" shorter than the 41 and 44 mag and 45 colt cylinders from 25-5 and later. The 45 acp cylinders are the same 1/8" shorter in front as well as about .035 shorter to the rear for the clips. The 357, 44 special, 45 acp and early 45 colts guns all have an 1/8" longer barrel extension to close up the B/C gap using their shorter cylinders. The stop notch and ratchet are all the same. The 45 acp cylinders have a thicker ratchet to head space properly with the clips. The ends of the extractor arms changed when the pins were deleted and the stop notch got longer with the addition of the endurance package. (See note below on endurance cylinders)
I have fit a pre model Highway patrolmen with a 45 colt cylinder made from a 29-2. I have also made 45 colt cylinders using 357 cylinders. I have also fit a 25-5 cylinder to a 1917 frame. While the overall shape of the ratchet teeth changed over the years, the shape of the surface engaged by the hand remains the same.
The metallurgy and heat treatment of the cylinders and frame no doubt improved as time went on. But, I find it extremely hard to believe that it makes any economic sense that any of the frames or cylinders of the same era got a better metal or treatment than the others. From a production tracking and liability standpoint it would be huge minus to do otherwise.
While I would not make a triple lock or early 1917 frame into a 44 magnum, I have made a 1917 into 45 colt and fired plenty of 255 gr- 1100fps rounds though it using more recent cylinders. It is the cylinder that fails not the frame and the cylinder will fail long before a load causes the frame to stretch.
Look at the old cap and ball colt dragoons that fired appox the same sized bullet at 1000fps with no back strap what so ever.
45 colt vs 44 mag cylinder wall and notch. The OD of the 45 colt case is .480 and the 44 mag is .457. A difference of .023 in diameter and .0115 in radius meaning the entire outside cylinder wall is that much thinner as well as the stop notch. The 44 mag runs at 36,000 psi a 45 colt at 25,000 psi has 30% less pressure. The stop notch cylinder area of 45 colt is exactly the same as that of a 45acp cylinder that is OKed for 23,00 psi 45ACP +P.
BTW go look at the thickness of the chamber wall on a 1911 running 45 supers at 28,000 psi. Then know a lot of guys are shooting a lot of 45 supers from 25-2s
One more note is that the endurance package and later cylinders had a longer stop notch and cylinder stop. It is located in the same spot as the previous guns. A endurance cylinder will work n a non endurance frame. But, a non endurance cylinder will not work correctly in an endurance frame with an endurance stop. Also in my opinion from an engineering stand point the endurance cylinders are weaker than the non endurance ones. Because the stop notch is longer you have a larger amount weaker area in a critical area of the chamber wall. If you do not believe that making the notch longer makes them weaker I advice you NOT to make the notch cut on a chamber full length and fire a round in it. A small thin spot in a pressure vessel get more support from the surrounding thicker area than a wider OR LONGER one
I spent 2 months earlier this year supervising the inspection and pressure testing tube exchangers. Worked with several API inspectors and 4 people who checked tube corrosion and wear using equipment that I will call sonic waves to get readings along the length of the tubes and another method called an iris that uses a small camera to visually record the condition of each tube. If tubes are suitable for continued use id determine by not just dept of corrosion but by area of corrosion and the amount of linear corrosion will cause rejection faster than radial.
