Hi guys,
I've had an ongoing problem with a 17-4 and I wonder if you have any wisdom to pass on.
It was brought in having had a new hammer fitted by another smith (broken hammer spur). It was light striking even with a 4Lb hammer pressure. I checked for the hammer hitting the rebound slide, sticking firing pin, hammer going fully down with no obstruction, firing pin protrusion, hammer hitting the safety bar....nothing. The cylinder-breechface clearance seemed a little excessive at .011" but the best I could do was take it down to .008" as that brought the barrel-cylinder gap up to .009" and I didn't want to make that any worse.
I did notice that the counter-bores in the cylinder are about .040" deep, which means that even with factory cylinder-breechface clearance the headspace is loose by SAAMI spec to say the least.
is this normal?
Can I fit a later model 617 firing pin which has a much better nose shape? (will the 617 FP bush fit a mod 17?)
any suggestions?
Cheers

Does it have the original mainspring? It might be too light. Is the strain screw tight? Has it been filed down any.
I have found that if I did not know if a part has been changed, I would try one that I knew worked well.

__________________
Tom
NRA Pistol Inst

No firing pin exchange. The later 617s use the same firing pin as the centerfires and they won't fit the earlier 17/617s.

The RFs need a heavier hammer fall than the CFs and are harder to get to consistently go bang with light DA pulls than the CFs.

Minimize wasted hammer impact.

Minimize the cylinder endshake.

Ream the chambers so the cartridges will consistently drop in so the rim sits on its' recess.

You don't want to waste any hammer hit pushing the cylinder forward or pushing the rd forward so its' rim is in contact with its' recess.

DO NOT bob or lighten the hammer.

Replace the strain screw with an 8-32 socket set screw and run it in 'til you get consistent ignition. I use Wolff reduced power mainsprings and the original strain screw is frequently (slightly) too short for good ignition with the RP spring.

Sorry if this is redundant...... have you checked the firing pin and f.p. spring? I wonder if the spring or pin may be damaged? You might also check for a bent cylinder alignment pin(s) or damage to the extractor, causing it not to seat fully.

My older model 17-1 specs are the same as you quoted.....the counterbores are approx .040" deep, and the rear gauge is .008".

__________________
Ret. LE, FA Instr, S&W Armorer

Thanks guys,
There is no endshake, no damage to the firing pin or spring, standard mainspring wound up to 4lb pressure.
The reason for asking about the 617 firing pin is that I have one here which is different from the mod 17. The 17 pin is round the 617 pin is chisel shaped, which will reduce the contact area considerably and therefore hit a more concentrated impact in my experience. The later pin has a slot cut in the flange which I assume matches with a rib in the retainer to maintain it vertical. So I figured I would need to use the later retaining bush. From the part number schematic I have it appears that the firing pin changed from #21343 to #21631 at the 17-8 and the bushing changed at the same time. I cannot say what the part number is for the pin that I have as it's not in a numbered bag.

I have a 617-1 with a 10 shot cylinder fitted. 617-1 was the first D&Ted 617 but was still square butt. I also have a 17-8. The 17-8 is my iron sight gun and the 617-1 has a C-More.

They both have the external cross pin for the firing pin bushing. I have two styles of firing pins for these guns. A hemispherical tip and a pointy chisel tip. The chisel tip looks like a hemispherical tipped pin with a reshaped tip. They interchange. The bushings are the same and the firing pin is free to rotate. The crosspin holds the bushing in place but does not index the firing pin, it is free to rotate.

I can't tell that there is any ignition difference between the hemispherical and chisel tip pins. I do know the stock firing pin spring is "plenty" strong and the reduced power spring supplied with the Apex Tactical Competition Firing Pin for FMFP centerfires is a perfect reduced power drop in or you can clip the stock spring.

The later 617s with no external bushing cross pin use the same hammer and FMFP as the centerfire FMFP guns.

The firing pin bushing is brass. My 617-1 I bought new in the early 90s and has 150,000+ plus rds thru it. It did at one point peen/deform the edge of the firing pin bushing (the bushings' edge is the firing pin stop and gets battered) and that deformed edge was catching on the firing pin spring, damaging it, and restricting the firing pin travel and the gun would have erratic ignition. Drove me nuts 'til I pulled the bushing out and saw what was going on and trimmed back the peened edge of the firing pin bushing and replaced the spring.