The original 1917's were made with mild steel. I would limit their ammo consumption to factory equivalent.
The newest 1917's were bought by the U.S. military were made by 1919, but commercial 1917's and the same gun for Brazil were made until 1946. Commercial versions were assembled with old parts until the new, 1950 .45 Hand Ejector replaced the old gun with a new frame incorporating short throw hammer and slide-action trigger block.
I have some qualms and reservations of depending on a mechanical device manufactured, sold and in use for 50, 60, as much as 82 years ago! Springs can loose their springiness, and any part can become more stressed and closer to cracking each time it cycles. 82 years of cycling can have worn many parts close to breaking.
The newer 1950 guns would be a better choice for a 4 inch carry gun. Steels are improved greatly and the fixed sights are wider and far more usable. It's a lot easier to find new/old stock action parts to repair post-1950 N frame guns than it is to find same for pre-WWII guns.
Downside of both old and newer (1950-1966) 1917s is cost. Martial 1917's in clean, original finish are growng steadily in value and the 1950 Hand Ejectors have always been pricey. That would discourage me from cutting one up into anything different unless it was already pretty ratty.
Desiring a smoooth, dependable .45 ACP fixed sight carry revolver, I would find a Lew Horton Heritage Series. They have 5-1/2 inch barrels but no internal lock and are as good a steel, heat treat and finish as any guns from that era. There are replacement barrels made in the Philipines floating around- buy one, have it cut to 4 inches, have the front sight replaced and save your original barrel. Probably the best fixed sight N frame made in traditional fashion you will find.
Another choice, the one providing new metal technology and requiring the least modificatioin, would be to buy one of the Model 22-4 "Thunder Ranch" .45 ACPs. It is already four inch barrelled and also has an ejector rod shoud, protecting the ejector rod and lockibg thge forward tip of it in place for shooting. Very wide, usable fixed sights. Yes, the M-22-4 has an internal lock but if you feel it compromises reliability and you want to carry it for protection, removal of the lock is not difficult.
These last two suggestions can eat Plus-P .45 ACP ammo all day.
I had one of the M-22-4's and found it to be a very nicely fit and finished sixgun. It may be just what you are after. It would take the least work to get what you want.
