There is no reason in today's world to rechamber any triple lock to .45 anything.
In fact the cylinder length is too short to reasonably use it for .45 Long Colt, and there are other technical issues including having to shorten the cylinder from the back end to convert it to .45 ACP.
You know, that makes no sense to me whatsoever. The big American double action revolvers were originally designed to shoot American rather than British cartridges - the exact same cartridges that Americans had been firing out of their single action revolvers since 1873. In other words: .45 Long Colt. When the British approached Smith & Wesson to fill military contracts (because Webley didn't have enough production capacity to make a
standard British Army revolver for every British or Commonwealth soldier who suddenly needed one) all S&W did was take its standard big revolver and modify it to shoot the shorter British .455 cartridge by leaving a step inside the chamber.
So the old .455 Smith & Wesson revolver (with commercial bluing & S&W brass-logoed wood grips but British proofs and 'sold out of Service' double-facing Broad Arrow marks on it) that I had a gunsmith convert to .45 Long Colt for me loads and fires factory .45LC cartridges with no problems at all... (Note: Before anyone screams too loudly in horror, that modification was done back in 1989. Most police forces still carried revolvers, and the big old milsurp Smiths were common as dirt up here - and almost unsaleable in .455.)
Now, I'm a little sorrier about my
other .455 S&W revolver that was
also converted to .45LC, because it has a
Canadian C-Broad Arrow marking, so it probably went overseas with the CEF in WW1. On the other hand, I suspect that conversion was done sometime back in the 1970s or 1980s too, and almost certainly by a gunsmith who was a revolver expert at someplace like a S&W warranty depot: changed from .455 to .45LC, adjustable rear sight and ramped front sight fitted, S&W oversized wood target grips fitted, and all the metal perfectly hot reblued.
Beautiful gun. And no trouble loading factory .45 Long Colt in it
either.
As I'm concerned, the main reason NOT to re-chamber a S&W Triple Lock or New Century from .455 to .45LC or .45ACP has
nothing to do with any technical problems with the calibre conversion and
everything to do with not destroying a piece of military history - much like one shouldn't convert an original full-wood SMLE into a sporter or use a mint P-14 as the basis for a custom wildcat rifle nowadays, even though that was the fashion 50 years ago.