The double cannelure brass if Winchester, WW or Remington, RP or Peters shows it was originally sold as 38 special flush wadcutter ammunition. The single cannelure if Hornaday or Federal was also wadcutter brass. I have always found better accuracy with sorted brass and I keep the cannelured and non cannelured separate. I believe originally the cases were thinner from the cannelure forward.

__________________
Front sight and squeeze