S&W Mainspring


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gunboat57
December 16, 2006, 08:17 PM
I get a fail to fire about once every 3 cylinder-fulls with my model 17-3. I noticed that the screw that tensions the mainspring wasn't turned in all the way. Should this screw be turned in tight? I'm thinking someone might've left it backed out a bit for a lighter trigger pull.

Tom P.

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JoeHatley
December 16, 2006, 08:19 PM
The strain screw should be kept tight. Your misfires should go away if you keep it bottomed out.

Good Luck...

Joe

Jim K
December 16, 2006, 08:30 PM
There could be other causes, but try turning in the strain screw all the way first. Note, though, that some folks tried to lighten the trigger pull by cutting down the strain screw so it would turn down flush but still be too short. If turning the screw in all the way doesn't do the job, look to see if it shows signs of having been ground off.

Jim

jad0110
December 16, 2006, 10:33 PM
I'm getting FTFs with my K-22 as well (though a bit less than half as many as you are experiencing), though my strain screw is tight. If the timing is correct and the lockup is tight, I'd say the next most likely cause would simply be a weakened mainspring. I was told by other members of THR that this could be the cause of my troubles, so I'll be ordering a new mainspring and strain screw in the near future.

Just tighten that screw down like any other and see what that does. Good luck!

Nice choice in a 22 I might add! ;) :D

Jubjub
December 16, 2006, 11:23 PM
Rimfire revolvers need a really good whack from the firing pin. After the first cylinder full, when loading you are pushing bore diameter bullets into a fouled bore diameter chamber. Chances are good that the firing pin blow has to push the whole round forward a bit before the rim starts to crush. Of course, the double action pull hammer fall is shorter and weaker than the single action.

Centerfire guns can be touchy, too. I have a Smith Model 66 that I have fired hundreds of rounds of .357 factory loads and handloads through without a hint of trouble. I made up a big batch of light lead bullet loads in .38 Special cases for my M10, which shoots them nicely, and tried them in the 66. Misfires every cylinder full firing double action. Maybe the rim is a scooch thinner, or something.

gunboat57
December 17, 2006, 09:46 PM
Thanks for the replies, guys. I'll try tightening down the screw first and see if that fixes it. You made a good point Jub about fouling preventing the rims from seating and not getting the full whack from the firing pin.

Tom P.

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