I had a ruger sr1911 with an identical casting mark and I had no operational issues with it and now a family member has it and neither has He... the front sight on the other hand is a different story.
His hammer will function fine, it just looks like sh## and is unacceptable for a PC gun IMO.
Yep. I'm guessing the new hammer will be the same too if a replacement comes. Welcome to modern injection moulding / casting
I would agree - my SW1911 PC (in 9mm - gasp) has exactly the same mark on the hammer.
I would have stripped it down taken a Dremal with a small ball stone and just cleaned it up "real pretty" and continue to shot the hell out of it.
I wouldn't do that. This way you reduce the working cross-section of the hammer. The force divided by the cross-section is called "stress". If that stress level happens to be slightly larger than the fracture strength level of steel used for the hammer it may fracture right away. I would never reduce the cross-section of any element which acts under force/stress. After all, all those elements were originally designed by engineers not by laymen.
Speaking from a "failure analysis POV, the rough texture of the blemish will allow stress to accumulate in the sharp valleys making failure more likely than if one polished the mark out.
Either way, the metal loss would be minimal and there is enough material in the hammer to likely not fail if left as is.
I mentioned about that in my post #7 but rather from a viewpoint of fatigue; that surface flow doesn't look to me like a notch that could introduce a substantial stress concentration
That depends how much material would be removed from the cross-section, minimal or not minimal; like I said I would never advise reducing the cross-section of a stress-carrying element. All in all, if I were the OP, I would ask for a hammer replacement ASAP. Case closed.



























