At the risk of starting a bloody argument, let me point out the Triple Lock doesn't work. That is, no one can show that guns made after S&W dropped the triple lock feature are less accurate, or wear out faster than guns with the lock.
One probable reason is that the triple lock is backward -- the actual lock is a pin in the frame pressed backward by a spring that locks into a hole in a tab dovetailed into the crane. The pin is an "object at rest" and tends to stay at rest under recoil, compressing the spring and partially (and sometimes totally) unlocking. When S&W came out with a retro-version about 20 years ago, they reversed that -- the lock was a ball bearing in the tab, and was pressed forward to engage a seat in the crane. With this arrangement, it locked tighter under recoil.
I'm your huckleberry.
With all due respect, your description is slightly incorrect. The 3rd lock of the Triple Lock is a tapered pin mounted in the underlug of the barrel, not the frame. In the photo below the arrow on the right points to that pin. The arrow in the center of the photo is pointing to the 'companion' (my own description) pin that mates into a hole in the end of the ejector rod, not much different than on most Hand Ejectors. This assembly is held in place by the two pins shown in the photo. I have never driven the pins out to see for sure, but my suspicion is that both pins are actually one 'U' shaped piece of steel. With one spring pushing both of them backwards.
Here is another view of the assembly.
The third pin pops into a hardened insert mounted in the yoke. There is no dovetail involved, the insert is held in place by screw at the rear of the yoke. The insert was case hardened for wear resistance. All the colors have worn off this one, but the hardness is still there. You can see the mark made by the 3rd pin as it rides up a ramped groove in the insert before popping home in the hole. You will also note in the first two photos that the pin is tapered, to help it find its way into the hole.
This 44 Special Triple Lock shipped in 1907. It is a very early one, the SN is under 200. Note that the caliber marking on the barrel says 44 S&W CTG. The 44 S&W SPECIAL CTG markings came about the next year.
Regarding the latch disengaging under recoil, the spring on the 3rd latch of this Triple Lock is stiffer than the spring in the latch under the barrel of the 44 Hand Ejector 2nd Model pictured below.
So if the 2nd Model, with its weaker spring does not unlatch in recoil, and it does not, why in the world would the stiffer spring of the Triple Lock allow the latch to disengage under recoil?
I have not put boat loads of rounds through the old Triple Lock, but I can assure you with my mild 44 Special rounds it had no problem.
I don't believe anyone ever claimed the 3rd lock made the Triple Lock more accurate, it was just a marketing strategy that S&W employed to help push sales of their new 44 Special revolver, the first N frame Hand Ejector the company made.
Roy Jinks states in his book
History of Smith and Wesson, published in 1977, that sales of the Triple Lock were slow, with only about 2,200 Triple Locks sold per year. So after 15,375 Triple Locks were made, the 3rd latch was dropped from production. The price of the Triple Lock at the time was $21. When the 3rd latch was dropped from production in 1915 the price of a 44 Hand Ejector 2nd Model was $19. This reflects the extra cost of manufacturing the 3rd latch.
Also, I have read reports that the British were not enthusiastic about the 3rd latch, believing that battlefield mud could enter the slot where the 3rd latch lived, disabling the gun. The more open design of the 2nd Model was less prone to being disabled by mud.
Regarding the ball plunger S&W is putting in some of its revolvers today, it is a cheap solution to get rid of the latch under the barrel. Dropping in a pre-manufactured ball plunger into the frame is very inexpensive. Less expensive than making up the complex rods and springs necessary for a traditional under barrel latch.
I ain't gonna get into the pissing match about how stout the loads should be in a Triple Lock. I only shoot mild handloads through mine. No need to over stress a gun that would be difficult to replace.
Most Triple Locks were chambered for 44 Special. According the SCSW calibers included 44 Special, 44 Russian, 44-40, 455 Mark II,and 38-40. 23 are reported to have been chambered for 45 Colt. 1226 are reported to have been chambered for 450 Eley. There were even a few chambered for 22 Long Rifle. The great majority, 13,753, were chambered for 44 Special.
Kudos to the OP for his find, shoot it in good health.
