S & W 686 Failure to fire

[Glenn]

I recently bought a used S & W 686-3. It has reportedly had an action job and does have what seems to me a very smooth and light trigger. I have shot a couple of brands of .357 and some handloads that I had for several years, without a failure to fire. I just bought 1000 rounds of Magtec 38 special for practice and have been getting 1-2 failures to fire from each 6. The primers are dented but not very deep. My first thought was that the ammo was bad but they fire without fail in my Ruger Blackhawk and TC Contender. Should I have the 686 looked at? Would this be a weak spring?

Glenn

[Guest Mugster]

Make sure the hammer spring is good and tight. Sometimes an "action job" includes not tightening the hammer spring all the way, or even worse, replacing it with a lower power hammer spring.

[Guest Grout]

Sounds like the strain screw is not tight enough.It is the screw in front of the grip strap.Make sure it is turned all the way in.

[Glenn]

I will check the screw. Is there any way to tell if the spring has been replaced with a weaker spring or will I just have to replace it with a new one.

Glenn

[Glenn]

sorry, double post

[Guest Mugster]

Somebody that shoots them a lot can probably tell by the feel. Or a trigger pull gage should tell the tale if you have a stock handgun to compare it to. The wolf spring kits are a big reduction, or can be.

I advocate removing the grips and eyeballing it a little before you try to tighten. I had to loctite that little thing a few times, kept backing out. Granted, my m19 is pretty old.

[Guest Matchguy]

Glenn,

I agree that the problem is probably ignition, but if the gun has chambers that are counterbored for the case rim, make sure the rim recesses are free of crud. If they get really crudded up they could cushion the case during hammer strike and cause a failure to fire. Also make sure the underside of the extractor star and its recess in the rear of the cylinder are free of crud.

Sometimes shadetree gunsmiths will reduce hammer tension by filing a bit off the sides of the mainspring, making it weaker. If you want to try a new hammer spring just to be on the safe side, Brownells only wants $5.86 for a new one. Look at:

Brownells - World's Largest Supplier of Firearm Accessories and Gunsmithing Tools+

One other thing to try is to remove the mainspring strain screw and see if it shows any signs of having been shortened during the action job. If the end in contact with the spring shows signs of filing or stoning, you'll need to get a new one from the factory. These two parts, the spring and strain screw should never be messed with in any way. Leave them absolutely factory stock.

I'm also a little suspicious that the ammo you're using may have inconsistent or out-of-spec rim thicknesses...i.e. the rims are too thin and keep the primer barely within reach of the firing pin about half the time. If all these things don't correct the problem, it will be helpful for the techs to know if the misfires are happening in the same chambers or not, and whether they're happening on single action, double action, or both.

Just some things to check out. Let us know what you find.

MG

[frankmako]

that is the problem with some trigger jobs. they are crap. i would get the wolf spring kit and drop it in. that should fix the problem. or you could get the factory parts from the net. i put a wolf spring kit in my model 19 and it has help the old girl with her light hits on the primers problem. trigger job done in 1973, springs just now gave it up.

[Glenn]

I removed the grip and the screw was tight. I removed it and the end does not look like it has been filed or stoned. The spring also does not look like it has been worked on. I did notice that the slightest release of pressure on the trigger causes the firing pin to back up slightly. I don't know if that is normal or not. I don't have much experience with double action revolvers.

I wonder if perhaps it is different technique between 357 and 38 loads and I am just easing off the trigger or something.

Glenn

[Guest Matchguy]

I don't think easing off the trigger would have anything to do with it, Glenn. Once the sear breaks contact the hammer is coming down regardless of any trigger action after that occurs. The only thing you might be doing that would retard the hammer fall is letting the support hand rub against it, and this is very rare on a Smith revolver.

I'm still hung up on headspace though. I had a M34 .22 kit gun that the factory never finished off the chamber polishing and the rounds wouldn't go in all the way unless you really pushed them in, so I got misfires from that. In another case I had to have an M19 cylinder replaced because of this kind of misfire and the reason was that the factory had counterbored the chambers too deep and I would get double action misfires at the rate of about 2 per 6 because the rounds were going into the chambers too deep. If hammer fall is ok, then I think something about the way the rounds are going into the chamber is keeping them too far away for the firing pin to reach. In line with this, if this is only happening with one brand of ammo, look at the rim thickness and make sure you are pushing the round fully into the chamber.

Jerry

[Guest Grout]

I did notice that the slightest release of pressure on the trigger causes the firing pin to back up slightly. I don't know if that is normal or not. I don't have much experience with double action revolvers.

Yes,that is normal.Unless pressure is kept on the trigger the hammer will not fall forward enough to protrude the firing pin.Also the chambers on 686s are not counter bored.