I have seen the "bulge" on 357 mag ,357 max,44 mag and 454 reloads .IPO it is caused by the sizing die not sizing to the rim because the shellholder is in the way.
I have never had chambering problems because of this.
If you think your cases have streches ,are you having to trim lots?
If you are triming lots of length off each reload I would be concerned.If not don't worry.
But if you are try this.
Take a paper clip bend a short L on the end ,and feel if there is a grove forming inside the case just above the case head. If so dicard the case.You may have a bad batch of cases. Or your reload is to hot or the gun has over sized chambers.
I have reloaded 357 mag for 20+ years and never seen a case head seperation. But it could happen.
Check it