You could also prime some cases and see what kind of results you get. It probably seems like a waste, but 100 primers is only going to cost $3. If the primers are not completely seated they will bind up and not pop reliably, the hammer pushes them the rest of the way into the pocket. And that would narrow things down on the cheap, depending on where you live (not in an apartment..) maybe not while being on the range. All the normal Be Really Careful stuff applies...
With light loads this is low danger with 38, one of the advantages of the full wadcutters is they go in farther to reduce capacity for more complete ignition with light loads. Don't try that with 40S&W, but 38 is pretty forgivable in this aspect.