The Colt Army Special wasn’t specifically chambered in either .38 Short Colt, or .38 Long Colt, but you can use either in a .38 Special chamber, which this revolver was (and is) chambered in.
As for shooting, the Old Fuff would point out that this particular revolver is almost 100 years old, and that should call for some special consideration. One point that is too often overlooked is the possibility of a sprung crane (the hinge part the cylinder swings out on). If the crane is badly sprung it is likely the bullet will hit the bore off-center, and this can eventually crack the barrel at the forcing cone.
To check, make sure the chambers are unloaded, and then close and latch the cylinder. Then while looking at the frame from the front, lightly press the cylinder to the left and right to see if the crane moves away from the frame, especially when you are pressing the cylinder to your right.
If so, it needs to be corrected before you do any shooting. Fortunately this is not difficult or particularly expensive, but it requires a gunsmith that is experienced and competent to do such work, and today they are rare birds. If there isn’t such a person in your area (and usually there isn’t) I suggest you try the Colt factory. It’s better to pay for good work then end up with a ruined gun. At the same time the timing should be checked to be sure each chamber “carries up,” or fully rotates from one chamber to the next and is locked by the cylinder bolt when the hammer is cocked. Be sure to check all of the six chambers. If they do not, don’t panic! Part of the reason may be a sprung crane, as mentioned above. Fix one and the other issue sometimes is fixed too.
Over the years Colt did make some internal changes, especially after World War Two,
so current Python parts often do not interchange. Finding the correct parts for an Army Special made in 1911 isn’t always as easy as it might seem. Also it should be remembered that at this time, each revolver was individually hand fitted, and most parts do not just drop in.
Ammunition: It was intended to use .38 Special cartridges loaded with 158-grain lead bullets, loaded to a muzzle velocity around 750 FPS, more-or-less depending on barrel length. More powerful rounds were not available or known at the time. Using more powerful ammunition is unlikely to blow up the gun, but they may accelerate wear and cause the gun to go out-of-time. This can usually be fixed, but don’t expect the work to be inexpensive.
Just hope when you reach the same age that this revolver is you’re in equally good shape.