Our "house defense" gun is a S&W Model 3904 loaded with Speer Gold Dots that run around 1,150. Hollow Points are illegal here, but I figure if it's come down to repelling boarders inside my house the Law no longer matters much. All the "forensic stuff" you see up North, that doesn't happen here.*
I noticed that the "chambered round" of the 3904, after being extracted and reloaded various times developed rings exactly like the one in your photo so I started always changing out the chambered round and moving it to the bottom of the mag and chambering a new one everytime I unloaded the pistol for either cleaning or to take out shooting. (After about 300 initial tests of the Gold Dot round, I no long ever practice with it and use a lead reload with a similar POI). Perhaps the rings on your rounds stem from the same cause.
*Many years ago, I did some work for the Mexican Army as a sort of "favor exchange". Later on, I was in a hospital in a city an hour south of here for some tests over a parasite I'd picked up probably years earlier in Honduras. While there, a Mexican Army Officer recognized me and asked me if I could come and "check something out" for them. I was lead to a room with a body on a gurney that had a sheet over it, and some technicians standing there with an X-ray.
"What kind of bullet is that?" asked the Army Officer, pointing to the X-ray. Looking at it I could clearly see what appeared to be a 158 grain lead round-nosed bullet turned a funny angle but pretty clearly "side-on" from the camera's point of view.
"Uh," I said, trying to be careful, "it looks like your standard Aguila 158 grain lead round-nosed .38 Special bullet."
The Mexican Army Officer clapped his hands together, turned to the techies, and exclaimed "We have a match!"
I have no idea who got sold down the river over that incident, but I have learned to be more careful before heading blindly into these things now-a-days. It ain't like you see on CSI down here.