Lightening up the 97b

[Lazarus]

For some time I have noted that the firing pin spring in the 97b is a whopper, and of course that made me start wondering why.  The only purpose I can think of for this gun to have such a heavy FP spring is to "allegedly" prevent slam fires.  The firing pin, given enough forward momentum, might continue forward during the chambering of a new round and protrude enough to fire the gun.  Since the trigger would be pulled during that time, the FP block would not prevent this from happening.  Has anyone ever heard of a .45 cal pistol slam fire from this cause?  Anyway, my goal is to lighten up the DA and SA trigger pull.  There is no reason this gun has to feel like a tank. Even with all the usual polishing and tuning, at some point, you have to say enough on the metal removal (sear and hammer).  That brings up the hammer spring, which has to be overly strong just to work the firing pin.  So, lighten up the FP spring a little, drop the hammer spring weight and the gun magically has a lighter trigger pull, without sacrificing any reliability, or becoming unsafe due to slam fire.  What is left is the question about whether the recoil spring now has to be bumped up another notch to compensate for the lighter hammer weight. Already we found that going from the factory 12 pounds up to maybe 16 pounds seems to be a good move, even without any other spring changes.  Any guesses now why they figured they could use a 12 pound recoil spring?  I'm testing mine out now, just in case I didn't do the physics correctly, but so far so good.
-Lazarus

[Walt-Sherrill]

If I understand the gun's function correctly (and I may not...), even IF the trigger is fully to the rear while a new round is being chambered, the slide moving to the rear reactivated the firing pin block, and the firing pin can't move forward again until the trigger is released and pulled again.

I don't think there's any risk of a slam fire with this gun.

I personally suspect that the firing pin spring is heavy because nobody really thought it mattered...  (Just the way they didn't seem to think a heavier recoil spring was needed.)

CZ seems to have a blind spot with regard to springs.

See if Wolff has some lighter hammer springs and go from there.

As you suggest, a heavier recoil spring makes sense.
(Test it with ammo...)

[Lazarus]

The 97b mechanism has a direct link from the trigger to the firing pin blocking plunger; so if the trigger is pulled the plunger is disengaged.  The blocking plunger idea tries to eliminate accidental discharges if the gun is dropped muzzle down.  The emphasis on "extra power" firing pin springs seems to come from the legal department and not the gun designers.  However I am certainly open to hearing from either party.  Wolff sends a firing pin spring out with the Sig P-series recoil springs that fits in the 97b and is lighter than the stock FP spring.  They also have a reduced power hammer spring pack that appears under the 75b pistols, (they are the same 2-1/2" long springs used in the 97b.)  Anyone know what the stock 97b hammer spring weight is?  I have to make a guess at about 22-25 pounds.  The 16 pound reduced power hammer spring has worked fine for me so far with misc range ammo.  The primer strike on the ejected cases looks normal.  I'm currently using a 16 pound recoil spring and will try the 18 pound as an experiment.
-Lazarus

[Lazarus]

Ooops.  It seems I am wrong.  The 97b has a feature that I was unaware of. The f.p. blocking plunger lever "resets" itself (clicks out of the way) when the slide trips the disconnector humps on the trigger bar.  That means that when the slide chambers a round, the blocking plunger holds the f.p. in place until a new trigger pull.  So, the stuff I said about the heavy duty firing pin spring applies even more, since they don't rely on the spring for any safety features at all.  Anyone else care to do some experimenting to find a good spring combination for the 97?
-Lazarus