"About 1903, Colt removed the shoulders from the chambers and changed their advertising to say that .38 Special could be fired in those revolvers."
Uhm, I may be wrong about this, but it's my understanding that when Colt did that they also started heat treating the cylinders to allow them to be used with .38 Special, something S&W didn't do for nearly 20 more years.
If it was originally chambered for .38 Long Colt, but has been reamed to accept .38 Special (apparently not uncommon), I wouldn't risk it with any loads other than those matching .38 Long Colt.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.