Cimmeron 357 is mangling primers.

[shawnba67]

A friend left me his cimmeron 357 (colt SA clone type) This pistol shoots 38sp just fine but when loaded with 357 the primers expand back and jam up the works. PLEASE DON'T SCREAM PRESSURE just yet all factory loads.
It appears that there is some pitting around the hole the firing pin protrudes through. of to the side and the primers seem to be bulging back into this area and then are "proud" and prevent the cylinder from moving easily. The firing pin itself shows no signs of flame cutting, it also doesn't look very worn. Its age is however info I dont have.
So is there any thing else that might cause these symptoms? I tried adjusting the screw that holds the center pin as it also acts as a hammer stop but one half turn stopped ignition completely so that seems unlikely.
Any ideas from the more experienced fella's?
Thanks Shawn

[Der Gebirgsjager]

Well, of course, a .357 does have more pressure than a .38. That having been said, your diagnosis of pitting around the firing pin hole is a possibility. A photo of the suspect area would be helpful. The original Colt had a firing pin bushing which could be replaced, but some of the clones lack that feature. If that is indeed the problem it could be addressed by micro welding up the pits and refinishing to original specs.

[44man]

Sounds like the hole for the firing pin is too large. Hammer mounted can be the worst. Dry firing too much can enlarge the hole.
The internal pressure in a primer can be huge. It is enough to cock the hammer. As the hammer goes back, the pin leaves the hole so the primer will flow into it. Much worse with reduced hammer springs.
Take slow motion video of a gun firing and see the hammer go back, even with over power springs.
Frame mounted pins are better, being captured but it still can happen if the hole is enlarged.
A punctured primer at some time in the past from a sharp pin will cut the hole.
The gun needs work.
The SAA had a hammer mounted pin, the .22 Scout had a frame pin. Some SAA guns had a sharp pin that punctured the primers and they would run full auto.
Today we have the .500 S&W that has doubled from inertia on the cylinder stop unlocking the cylinder to rotate backwards and hammer bounce taking the hammer back far enough to fire a round if it is there.

[runfiverun]

the bushing.
the pressure.
the rim has no where to go.
think it through.