This afternoon we went out, and tried the 552 (replacef the hammer spring), I stoked it with 10 rnds Federal silver box, cycled in the first round, which fired, the second didnt and neiter did the 7th & 9th rounds tried.
So 7 out of ten fired!*
Then tried another six and only one fired, then I tried*some old CCI minimags and every one of them duded out on me.
After getting back to town, I removed the barrel/bolt unit.
While out I noticed some battering on the side front Left side of the hammer, its fresh from hitting something and killing off the hammer blow force.
Too a photo of the bolt and barrel inverted so the firing pin was hanging down out of the bolt, then tipped it down so the firing pin gravity dropped into the fired position.
Then the odd dent on the forward Left corner of the hammer.
Last couple photo of me trying to get a hammer side play deflection.