The picture I saw of the firing pin looks like they way they did the firing pins on the Browning 1886s. It amounts to a two piece firing pin/sleeve arrangement that looks like its supposed to be less prone to dropping and firing, the center part has to move some before the outer sleeve moves and allows the center part to go all the way forward. It seems more complicated than neccesary, but seems to work fine in the Browning 86's I have.
I had heard it has a standard half cock hammer and no other widgets like a cros bolt or tang safety.
Uberti has been making 357 cal 73's since the mid 70's that I know of. I suppose you could wear one out, but I'd be willing to take the chance. A 357 carbine in a 73 would be a cool and useful gun, though the short rifke is the same size, if a touch heavier. A 44-40 may be more useful in the field for larger critters, but the 357 would be more practical in finding ammo if need be, and matching more modern sixguns that more folks have. A 45 Colt carbine could be good also.
The bolt thrust of the 357 round is higher than the 44-40, but not as much as first appears from chamber pressure alone. The smaller base makes less bolt thrust for a given unit of chamber pressure.
This was posted by COSteve on the leverguns forum.
Win 1873 Bolt Thrust Calculator - Case radius ² x pi x max pres = Bolt Thrust (BT)
Original Winchester 1873 calibers
Caliber.....Case Dia.....Max Pres.....BT (lbs)
.22lr..........0.225.......24,000.........954.3
.32-20.......0.354.......16,000.......1,574.8
.38-40.......0.465.......14,100.......2,394.5
.44-40.......0.471.......13,500.......2,352.2
Compare those to more modern cartridges
Caliber.....Case Dia.....Max Pres.....BT (lbs)
.38 Spl........0.379.......17,000.......1,917.9
.38 Spl+P.....0.379.......18,500.......2,087.1
.357 Mag.....0.379.......35,000.......3,948.5
.44 Spl........0.457.......15,500.......2,542.5
.44 Mag.......0.457.......36,000.......5,905.1
.45 Colt.......0.480.......14,000.......2,533.4
.45 Colt+P....0.480.......23,000.......4,162.0
.45 Colt+P+...0.480.......25,000.......4,523.9
A point worth mentioning when dicussing the toggle link actions and relative strength, many seem to think the bolt would come back in your face if overloaded. I've never heard of it happening with any lever gun that was overloaded or worn out, a 73 in particular. The bolt itself wont make it thru the reciever, its installed through the top of the reciever, only the firing pin extension comes through the back of the frame in a 73. If you managed to grossly overload one to the point the action couldnt handle it, the bolt would stop at its open position when its shoulder hit the rear of the action window, the links and pins may be toast, and the sideplates come off, but the bolt isnt coming back any farther than that. The barrel is the usual weak point in lever actions, with some dramatic action disassembly occasions, but the bolt still doesn't come back in anyones face. What generally happens if overloaded in use (not a case full of bullseye, but just more than the action will stand over time), is the actions tend to stretch and become non-functional. Some Marlins bulge the sidewalls out where the bolt rides in it when overloaded, with the same result, the action becomes non-functional.