Three places where Dykem rubbed off:
Upper right leading edge of the hammer to the side plate.


Right side top of the hammer block.


Hammer nose - mostly right side.

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	36-1_2024-03-06_Hammer_rub_15.jpg (269.9 KB, 83 views)
	36-1_2024-03-06_Sideplate_10.jpg (222.1 KB, 96 views)
	36-1_2024-03-06_4_Hammer_Nose.jpg (243.7 KB, 93 views)
	36-1_2024-03-06__Hammer_block6.jpg (69.4 KB, 92 views)

The rub mark on the sideplate indicated with an arrow is from the front leg of the bolt.





Carter

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Ret. LE, FA Instr, S&W Armorer

Thank You!

Checked the main spring force on the hammer as shown here.
https://smith-wessonforum.com/141763281-post12.html

It's a little different than Kuhnhausen but makes more sense to me.
Just about 3.5#
I used a coat hanger, milk jug with water, and postal scale.

That's 56 ounces. With Federal or Winchester primers you would probably be OK. With your ammo (primers), you probably need to be in the 64 to 70 ounce range.

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protocalldesign.com

Of course I had to recheck my measurements after you posted that.
3# 12 oz lifting very slowly the hammer held.
3# 13 oz. and it did not.
So 62 oz.

Right below what you're saying is needed for consistancy with the harder primers. But close enough makes me hopeful that a new factory spring might do the trick.

I didn't check before I took the Precision One to the range with me as an alternative to the Fiocchi. Yep They use CCI primers.

CCI and Remington are the hardest primers. I don't know how all the foreign primers rate.

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protocalldesign.com

Finally got to do a little testing at the range.
So far, so good double action with

20 rounds Browning 130 gr FMJ
20 rounds Remington 158 gr LRN

Dykem is still on the right side of the hammer (did not get scraped off).

Next test will be the Fiocchi or Precision One with the harder primers.

Attached Images

36-1_2024-03-27_1810r.jpg (123.2 KB, 4 views)

and with the Fiocchi 158 gr FMJ the failures to fire returned.
Most of today's shooting was single action as I was checking point of impact vs point of aim for 10, 16, and 25 yards. First 5 DA were fine. But there was a failure to fire on the first hammer hit for a cartridge in each of the 3 cylinders fired double action at the end. Second hit they fired.

Based on the hammer spring check above, it seems the most likely cause and solution will be a factory hammer spring.

I've read through this thread with great interest and am hopeful that a new, full power hammer spring takes care of it. If you PM me your address, I'll send you one.

ETA: grammar improvement

Quick update:

Thank you Mercury!


The new black spring is slightly longer. If everything else is the same as the old black spring (and it seems very close), then assuming a modulus of elasticity of 12x10^6, the spring rate of the old black spring is around 13 lb/in, new spring is around 14 lbs/in. That could be the difference between using a good vernier vs. a cheap dial caliper. However the new one's free length is longer, so it will apply more force for any given compression.
The spring rate of the new silver spring calculates to be closer to 17.5 lbs/in. Length is between the old black and the new black.

I bought a good used round stirrup/hammer strut. Installed that with the new black spring. Also took a one little burr off the side plate where it was just scratching the hammer. But that won't effect the weight test.


Testing the result of the spring change using the same method as previously posted, result was only another ounce at best. So its up to 59 oz.

However, the difference between primers firing and not firing has been the difference between single action and double action. The static force as measured doesn't change between SA and DA. So its a good reference point, but doesn't tell the whole story.



Next step will either be to test the installed spring and stirrup with the Fiocchi, or change to the silver spring and measure the hammer force. Depends on whether I go to that range before I get time in the shop.

Attached Images

	36-1_2024-04-19_1998cr-Springs.jpg (194.0 KB, 25 views)
	36-1_2024-04-19_1993-Spring-working-length.jpg (80.7 KB, 24 views)

Annecdotal but perhaps indictive of harder primers.


Two reviews of Fiocchi 130 gr FMJ at Lucky Gunner have failures to fire. Both were using S&W Model 19. Total of about 8 reviews that state or suggest the person had actually used the ammo at time of review.

The spring wire diameter makes a big difference, too. A couple thou. larger wire diam. will be a lot stronger spring, all else being equal. If all the springs have equal wire gauge, they will be essentially the same.

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protocalldesign.com

You're welcome Matt_X, I'm happy to help.

I included the 2nd silver-colored spring because it felt stiffer and you may end up needing a stronger one.

If it where mine, I wouldn't feel that it was fixed until it had zero failures-to-fire, so range testing is necessary.

Please continue to keep us posted and good luck.

The bright spring certainly has the highest spring rate and will apply more force through the working range. At some point I will try it just because I'm curious if it will have any noticible impact on the trigger pull.

My measurements for working range of spring are as follows:
Hammer in rebound 1.322"
Hammer at Single Action full cock 0.984"
Hammer fully forward (with no cartridge) 1.347"


The wire of the old hammer spring was 0.033" dia. and the wire of the new black spring is about the same (as mentioned I don't fully trust the dial caliper I have at the house). The wire of bright spring measures .0345 but I think its .035" wire. This because .033 and .035 are standard piano wire diameters.

The other difference of note is the the black springs have 27.5 coils while the bright spring has one less coil. Other differences are minor. For example the ends are cut and ground although the new black spring end is more tapered than the other two.