Can you replace the bobbed hammer in a 3rd gen 45 automatic with a 2nd gen 39 spurred hammer? The action is SA/DA.

For morale purposes (not an expert, here) till someone who knows comes
by, I think you have to match hammer & sear *type*--as in, a MIM hammer
needs MIM sear.

AFA any requirement for fitting them, I won't speculate.

The hammers are structually the same, so technically, yes. That said, you will get better feel and feedback in the action itself, especially in DA if you use a spurred, 3rd gen MIM hammer instead. (opinion)

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Ret. LE, FA Instr, S&W Armorer

Yes, the hammers should interchange, but be advised, the 2nd gen hammer will have a "half-cock" notch while your 3rd gen hammer does not, and you will definitely notice the "hitch" during the double action trigger pull.

The half-cock notch was a safety feature that was rendered redundant when the firing pin safety was added to the 2nd gen models.

That DA trigger pull hitch might seem insignificant, but gun writers and owners found it so objectionable that S&W eliminated it for the 3rd gen pistols.

John

I keep hearing it repeated that MIM hammers must be mated with MIM sears.

And I have been guilty of repeating it a time or two, myself.

But I can find no concrete evidence to justify that belief.

It IS true for the early DAO models, but they had a different sear and hammer geometry.

John

For learning porpoises (not argumentative)--what does the
annotation on MIM sear mean?

Attached Images

MIM Sear.jpg (30.4 KB, 52 views)

Actually, I think that is an astute question.

I believe it means what I alluded to earlier, that the MIM sear was NOT to be used in the early (non-TSW) "DA" (DAO or Double Action Only) pistols with a non-MIM hammer.

These early DAO pistols had a different shaped sear and hammer notches that were unique to the DAO models.

When the DAO pistols went to a MIM hammer, S&W changed the location of the hammer notches so that a single (MIM) sear could be used for all models, DAO and TDA (DA/SA).

This was a message for assemblers and armorers to save time and confusion.

John