Case Head Exits Rifle

[MEHavey]

The hammer moved it back into battery, Jim, as you still had the trigger pulled and the sear was disengaged.

Put the full-up/stronger spring back in.

Believe it or not I had a similar problem last week with a S&W Model-19 which had had its mainspring cut down to smooth out the action. Primer setback could then push the hammer to back out enough to allow primer flow right back to/into the firing pin hole and lock up the cylinder on every full-up/40,000psi .357Mag load.

Putting the original mainspring back in solved the problem.

In the Model-19 it was an annoyance. With the rolling block's dependence upon hammer position to lock up the breech, that sounds like a potentially fatal annoyance.