The practice of shooting .32 ACP in .32 S&W Long revolvers is probably as old as the .32 pistols and revolvers are.
I never rcommend anyone shoot ammunition for which their firearm wasn't chambered, but I have done this myself and it didn't seem to hurt anything.
It shot several inches lower on the target at 25 yards than did the correct Long cartridges, though.
But it was better than nothing to shoot in the gun, at the time.
Your Model 31-1 is a fairly modern revolver, strong as small-framed .32 Longs are concerned, anyway, and should be "safe" if the gun is in good shape. I wouldn't to it in an old top-break.