I own a Hopkins and Allen police safety. It is not marked for the caliber. When I bought it , I got it for a very low price because they knew it was 38 caliber, but a 38 special was to big. I bought the gun and at another shop I bought a box of Smith & Wesson 38 S&W cartridges they fit in the chambers but they were. Very tight. Later on I picked up 2 boxes of 38 short in Reminton brand and on another occasion I bought a box of Peters in 38 Colt New Police.
As I compare these cartridges I see the following;
The 38 S&W fits, but unfired cartridges will not eject when the gun opens. Each cartridge must be pushed out of the chamber with a dowel rod. The case for the 38 S&W is longer than the short or new police.
The 38 New Police fits the like one would expect it to. The case of the New Police is a little over an 1/8 inch longer than the 38 Short case and about 1/8 of an inch shorter than the 38 S&W case.
The 38 Short fits the chamber like you would expect it to also. The case for the 3/8 short is 1/8 th of an Inch shorter than the New Police and a 1/4 inch shorter than the 3/8 S&W.
I have shot both the Colt New Police and the 3/8 short with good results. I have not fired the 3/8 S&W in the revolver because it don't fit correctly. In comparing these 3 cartridges, they are 3 definently different cartridges. I also am not claiming that I am an expert regarding these cartridges. Nor have I tried reloading any yet. And that is a result of not having any info on them. Info on them seems to be scarce at the best of it. So I am passing on what little I know. If any of you could explain to me about heeled bullets and such, I would appreciate it.