S&W 1917 light primer strikes

[bobmitchum]

I picked up a couple of nice examples recently, and took both the range today. Both had been cleaned, thoroughly.
Ammo was new Winchester White Box.

First one was flawless, couldn't ask for better ...

Second one was consistently giving me light primer strikes,
2-3 rounds per cylinder, generally two rounds per cylinder.

I checked the strain screw - and it was as tight as I could comfortably make it ... matter of fact I am pretty sure it was ALL the way in ...

All of the cases show the firing pin impact, but the unfired cases are clearly getting less impact - something along the lines of 30% less deep/defined then the fired cases. Photos to follow...
both of the cylinder/cases and the strain screw/spring ...

Any suggestions or counsel here would be greatly appreciated.

I was going to see if Wolff made a stronger mainspring then stock, and order one of those.

Both were fired using full moon clips, and it didn't occur to me to try either or both without them, until I was driving back home.

Again, welcome any suggestions ...

 

[moosedog]

Try some other ammo and also check that strain screw to see if it has been filed down to make the trigger feel lighter. It can be tight but still have been shaved down on the main spring contact end.
Also check the edges of the main spring to see if it's been filed down. Both of these things are sometimes done to lighten the trigger pull. If it continues with other ammo, you might want to replace the main spring if it feels light. The changing of the trigger return spring and main spring were the "trigger job" in a bag of the 70s-90s.

 

[deyomatic]

See if it's the same chambers each time? Also, are the strikes centered on the primer?

 

[bobmitchum]

Excellent suggestions, thanks.
Photos as soon as I am able, but they "seem" centered to me.

 

[Muley Gil]

Lay your moon clips on something that is absolutely flat to check and see if the clips may be bent.

 

[Nightowl]

Trouble shooting is a matter of checking things out that could cause the problem. On light strikes, it is almost always, it seems to me, a mainspring issue, given everything else is good. In this case, the first thing to check would be endshake. Is there for an aft movement of the cylinder. If not, I would take the mainspring from the "good" gun and put it in the one having misfires. If that does not solve the problem, then put the original springs back in place and exchange the strain screws. If that fixes it, then return the good strain screw to its original gun and get a new mainspring strain screw.

If none of those fix it, then you have a bigger problem and some hands on by a gunsmith may be next.

 

[Nightowl]

Trouble shooting is a matter of checking things out that could cause the problem. On light strikes, it is almost always, it seems to me, a mainspring issue, given everything else is good. In this case, the first thing to check would be endshake. Is there for an aft movement of the cylinder. If not, I would take the mainspring from the "good" gun and put it in the one having misfires. If that does not solve the problem, then put the original springs back in place and exchange the strain screws. If that fixes it, then return the good strain screw to its original gun and get a new mainspring strain screw.

If none of those fix it, then you have a bigger problem and some hands on by a gunsmith may be next.

 

[Wiregrassguy]

If the light strikes are on the same side of the cylinder opposite the chambers that fire, your yoke arm may be bent. If you know how to check runout, you can use that technique to see if the cylinder is rotating parallel to the hammer nose and not wobbling.

 

[Baltimoreed11754]

Swap the strain screws and see if it makes a difference. If no improvement swap the mainsprings.

 

[StrawHat]

Another way to check if the strain screw has been shortened is to lengthen it. Back it off until you can slip a spent primer (remove the anvil first) over the end. Tighten the screw to push the primer against the mainspring. Your strain screw is now longer by the thickness of the primer metal. If this works, order a longer strain screw, or get a set screw from the hardware store.

Kevin

 

[bobmitchum]

This is GOLD ... thank you, all !
I will start with the simple stuff, and report back.
Appreciate all of the wise counsel, here.

 

[gunsnrovers]

Definitely suggest you start with a strain screw. On a model 22 I recently picked up, the previous owner ground down the tip and then put a leather spacer between the screw and the main spring. Gave me a fit until I figure it out. I looked all the regular places and never thought to measure the actual screw.

 

[ddixie884]

The primer on the strain screw trick must have worked. No new post...........

 

[crsides]

I agree with other posters above, mainspring, then strain screw. Might check for a damaged firing pin.

 

[Jack Flash]

Very good information from this group. I hope Bob Mitchum returns with a progress report.