The majority of S&W customers do not want to pay for the QC that would consistently catch 2 bad pieces out of a shipment of 5,000. Some PF members might, but when it's time to vote with cash, even many PF members are tightwads. It's one of the reasons why guns like an 870 Wingmaster are no longer common. It's why the 870 Express is getting clobbered - A similar gun from a foreign manufacture with less QC is 30 bucks less at WalMart and selling like hotcakes.
How much manufacturing experience do you guys have? This is like when people say "Cops should shoot the gun out of the bad guys' hand", without understanding much about being a cop. I love vertical integration in manufacturing, but it's unlikely that S&W is going to become a better SME on MIM than a MIM manufacturer. So outsourcing makes sense on a process that S&W doesn't have 150 years worth of established knowledge base. If S&W made that part in house, it could (probably would) be worse.
It's hard to believe that something as important as the hammer can be sold by a third-party vendor for $10.49. How many companies have made profit on that part, and it's still 10 bucks? Unless MIM has advanced a long ways in the 10 years since I dealt with people in that industry, that is a horrible geometry to make in MIM. I suppose those ejector pin intentions visible on the side view could be from the die that makes the wax patterns for investment casting, but at that price I doubt it.
Even if they did 100% NDT, based on a LOT of experience with customer returns of 100% inspected parts (or 200% or 300% inspection - 100% inspection multiple times), unless it's robotic/automated, it's still only about 90% effective. That's why when customers care, they specify and pay for automated/robotic inspection on critical parts.
Are you sure that's MIM? The pics at the link show tooling marks from a lathe, and that geometry lends itself to a bar fed lathe or screw machine. It could have been made from bar, but overhardened enough to become brittle. If you still have the broken parts, send them to me and I'll section them and post pictures of the microstructure(I'm a Metallurgical Engineer).
https://www.midwestgunworks.com/page/mgwi/prod/pin-6