Can a forged hammer be used with MIM components

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ΜΟΛΩΝ ΛΑΒΕ

No.
You can't install a MIM hammer or trigger in a pre-MIM revolver, and you can't install forged parts in a MIM gun.

One reason is that forged hammers have the firing pin on the hammer and MIM guns have the firing pin in the frame.

Other than that, the parts simply aren't comparable between forged and MIM guns.

Actually some you can and some you can't. You can put a forged trigger, and rebound slide in a MIM gun. I've done it mainly because the MIM trigger tends to pinch my finger. MIM versus forged hammers are a different story because of the location of the firing pin.

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S&WCA 1729

The issue isn't MIM vs forged but whether it's a hammer or frame mounted firing pin. My FMFP 627 that came with a forged hammer (the only gun I know of where there were both forged and MIM hammers, both FMFP) now has an MIM hammer in it and I've put MIM rebound slides and .400 smooth MIM triggers in a number of "forged" HMFP guns.

The biggest fitting issue when replacing forged triggers with MIM has been trigger / cylinder stop engagement, aside from the usual sear fitting. With the MIM trigger an MIM cylinder stop has frequently been required.

I have to disagree with the "Other than that, the parts simply aren't comparable between forged and MIM guns." statement.
Some forged and some MIM parts ARE interchangeable, i.e. the .312 MIM trigger will work in the older guns, IF you buy all the parts needed. I have done this many times. I have also replaced certain forged hammers with MIM hammers, the main thing to consider is if the gun has a frame mounted firing pin.
As far as the metal (MIM vs Forged) is concerned, try drilling a MIM part, you will see it is as hard or harder than the surface hardened forged part.

IIRC, I think it was a 625-6 MG I saw that had the MIM hammer and a forged trigger.

At the transition from forged parts, HMFP guns to the MIM parts, FMFP guns S&W sent out a bunch of guns with an odd mix of parts apparently using up what they had.

They've always done this but during the forged to MIM transition it was probably most obvious.

Big 10-4.
I've seen several with mix-matched parts but I think I've noticed more 625-6's. Some with all MIM and some with forged triggers.

Good news.......

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ΜΟΛΩΝ ΛΑΒΕ

Screwed that one up...sorry.
Was thinking of original type forged parts versus current MIM parts.