here's a picture or two
of primers from a load that was about 17-18 gr. of AA#7 under a Lead 140--in a 38SPL case. It was a reloading error, not a double charge--and it took some minor detective work to determine what had happened (other than the reloader--that's me--not being familiar with AA#7 recently).
http://www.pbase.com/jfh1945/image/82483587
As you may know, a 38 SPL+P load tops out at 18,500--some one else has calculated the pressure for these cartridges was 55,000 to 72,000. I shot a cylinderful in a S&W 640--the 24oz SS snubby in .38/.357. The recoil was awesome, but entirely controllable--sort of like a tsunami coming at you.
The gun held together, obviously, and I even shot another 80 rounds or so of low-medium .357 loads, but with sticky extraction. Examination by my gunsmith revealed a stretched cylinder (see the other pictures) and S&W ended up putting a new cylinder and barrel in it.
The primers are WSPs--and they really don't look that bad, IMO. The brass was new Starline (maybe fired once), and the heads separated when I tapped them gently with a range rod. Note that you can even still read the case head easily.
I've seen primers like this before, and pictures of others that looked much worse. Somewhere there are pictures from the .223 loads one of the Armed Forces team uses in long-range competition--and those are melted and the case heads smeared.
The point is, as others have said, I now am not convinced one can read primers very readily for overpressure signs.
Jim H.