Light Strikes With S&w 686

[professor]

OK. I've been shooting this S&W 686 with both .357 magnum and 38 Spl ammunition [my loads], using Federal primers/brass and varying amounts of Titegroup behind 158 RNL and 130 FMJ ball bullets. I'm shooting this ammo with moon clips, and primers are not high.

The last couple of matches, I've had light hits on the 6th shot of a clip multiple times. First 5 shots nicely consistent, centered, and fire with no problem. Sixth round hit is centered, but too light to set off the primer. The last two times it malfunctioned was on a classifier with shoot 6, reload, shoot 6. It malfunctioned on the same target both times. After the second malfunction, I tried 6 more pulls of the trigger, just to see if it would fire the second time around. Nope. I figured the misses had blown my score on the classifier anyway, so it wouldn't hurt to see if it would fire with a second hit, and if it didn't fire, it wouldn't add any time, either.

This revolver has the firing pin in the frame, not on the hammer.

It hasn't malfunctioned in the middle of the moon clip, just on the 6th shot, and just on rapid fire strings. [Rapid for me, that is. Maybe .25 splits]

Yes, I've backed off the mainspring, but never had a problem with missing shots. Also, the position of the screw is secured with blue loctite, so it hasn't backed out even more, lightening the hammer strike.

Suggestions?

[JohnRodriguez]

maybe your bullets are pulling enought the lift the case off the cylinder on the 6th shot. What are you using? 38spl brass ro 357 brass, a pulled bullet would be more likely with a 357 case. check your moonlips on a plate of glass to make sure that they are flat, and don't have one finger that is twisted. remove your firing pin and make sure there is no buildup in the frame

[bountyhunter]

If it only does it on one position of the clip, that pretty much proves the problem is associated with the clip or something that is happening to it.

[pskys2]

If this is happening with all of your moon clips it's not the clips. If it's only one or two, chuck 'em or get a tool to repair them.

You don't have a broken Extractor Star, or some other anomaly do you? Have you checked the FP & Spring for damage or crud?

Your mainspring could have slipped on the strain screw. Try using a trigger pull gauge to measure your DA trigger pull. Then adjust your strain screw in 1/2 turn, measure again and go shoot it. Make sure the MS rib, if it has one, is centered on the strain screw. Then back it off a 1/4 and recheck it.

I usually try to measure the final distance and grind a screw down to it, so that it needs to be bottomed out. I don't like relying on Loc-Tite.

[Thomas Moore]

i agree with pskys2, i have a couple of ppc revolvers with jerry miculek's S&W trigger kits. measure then grind the screw appropriately so it can be bottomed out.

[Randy Lee]

Greetings,

You might check to see if the moonclipped rounds are springboarding your cases. On .357/.38 spl guns, the case heads should rest solidly against the cylinder face when the cylinder is pointed down towards the ground. If a moonclip is bent, or even one of the fins, it can cause misfires by dampening the impact of the firing pin.

Other possible causes- overly chamfered charge holes, uneven cut of the cylinder face during the moonclip modification.

I didn't do the moonclip conversion, did I?

[professor]

Thanks for all the suggestions on things to check. I've been out of action since my original post starting this thread [Daughter #2 produced a new granddaughter on May 10th, daughter #3 got married on May 20th, and I needed a week to recover].

The moonclip conversion and chamfering was done on this cylinder when it was part of a S&W 586, and I hadn't had this malfunction in that gun, ever. When I got the Model 686, I swapped in the converted cylinder rather than have another moonclip conversion done.

The last match I shot, I had this malfunction with 5 different moonclips, and no problem with the other 13 clips used at the match. I checked all my moonclips for flatness at the beginning of this shooting season, and I'll do that again, but I don't think that is likely to be the problem, as I don't think the malfunction would always happen on the last shot of the 6. I also examined the light-hit shells, and there was no indication of high primer, or springiness on the face of the cylinder.

Also, I'm shooting 38 Spl brass, almost all Federal, and the shells that did not fire do not show evidence of bullets pulling out.

Mainspring is centered under the strain screw. Strain screw is tight (with the blue loctite). It didn't misfire on every moonclip's 6th shell, but it did happen on speed shoots.

I haven't had time to get inside to check for crud or whatever surrounding the firing pin, but that's going to happen before this weekend, with test firing scheduled for Sat, and another match on Sunday. I'm thinking that if it was simply crud buildup, then gradually I'd experience the problem with more than just the last shot of a clip.

I think a cylinder-related variable-sized gap between the shell head and the blast shield would result in these misfires occurring at random locations on the moonclip, not on the 6th shot exclusively. But I'll check for that, too.

Star extractor works fine, and is not cracked, bent, or otherwise appears defective.

Right now, I'm thinking it is related to increased friction of the firing pin in the pin guide, which gets worse when the metal/crud/whatever heats up from rapid fire. At this point, this gun has had less than 3,000 rounds through it, so I don't think its a problem with firing pin spring fatigue.

I haven't had a trigger job done yet. Randy, is there anything that would cause the trigger hammer to hit the firing pin with less effort after multiple shots?

Hopefully, I'll have more information after the weekend's testing and shooting activity.

[Bubber]

Thanks for all the suggestions on things to check. I've been out of action since my original post starting this thread [Daughter #2 produced a new granddaughter on May 10th, daughter #3 got married on May 20th, and I needed a week to recover].

The moonclip conversion and chamfering was done on this cylinder when it was part of a S&W 586, and I hadn't had this malfunction in that gun, ever. When I got the Model 686, I swapped in the converted cylinder rather than have another moonclip conversion done.

The last match I shot, I had this malfunction with 5 different moonclips, and no problem with the other 13 clips used at the match. I checked all my moonclips for flatness at the beginning of this shooting season, and I'll do that again, but I don't think that is likely to be the problem, as I don't think the malfunction would always happen on the last shot of the 6. I also examined the light-hit shells, and there was no indication of high primer, or springiness on the face of the cylinder.

Also, I'm shooting 38 Spl brass, almost all Federal, and the shells that did not fire do not show evidence of bullets pulling out.

Mainspring is centered under the strain screw. Strain screw is tight (with the blue loctite). It didn't misfire on every moonclip's 6th shell, but it did happen on speed shoots.

I haven't had time to get inside to check for crud or whatever surrounding the firing pin, but that's going to happen before this weekend, with test firing scheduled for Sat, and another match on Sunday. I'm thinking that if it was simply crud buildup, then gradually I'd experience the problem with more than just the last shot of a clip.

I think a cylinder-related variable-sized gap between the shell head and the blast shield would result in these misfires occurring at random locations on the moonclip, not on the 6th shot exclusively. But I'll check for that, too.

Star extractor works fine, and is not cracked, bent, or otherwise appears defective.

Right now, I'm thinking it is related to increased friction of the firing pin in the pin guide, which gets worse when the metal/crud/whatever heats up from rapid fire. At this point, this gun has had less than 3,000 rounds through it, so I don't think its a problem with firing pin spring fatigue.

I haven't had a trigger job done yet. Randy, is there anything that would cause the trigger hammer to hit the firing pin with less effort after multiple shots?

Hopefully, I'll have more information after the weekend's testing and shooting activity.

I reread the posts and am wondering if you have checked the endshake. Had a similar problem with misfires. And if it does it only on rapid fire, well if it weren't for seeing hits on the primer I'd say Skip Chambers was paying you a visit. Were the light hits center?

[revchuck]

Endshake is a possibility, but I'd also look at headspace, since the cylinder isn't original to the gun.

[professor]

All hits were centered, but light. I used to have trouble with short-stroking the trigger, causing cylinder skips and some off-center hits, but hopefully THAT problem has gone away after concentrating on eliminating it during dry firing drills.

I'll be checking end shake and head space.

[Rover]

I agree about checking endshake and headspace. Might check the rear of the cylinder to see it is machined true and firing pin protrusion, also. Cylinder & Slide also makes an extended firing pin for the frame mounted guns if protrusion is a problem but I would not think that would be the case 1/6th of the time. At any rate with the sideplate off it is easy enough to take the pin out and clean it and the channel.

[aerosigns]

Prof,

I don't know if this will relate to your problem, but I had something like this occur years ago with my 686.

I would have a problem towards the end of fast 6 round strings. The problem ended up being 'Heat'.

For me when I would fire a fast string, heat in the gun would rise, and for me cause the crane to swell. As soon as I was done, and looking at my gun the heat would disipate and things would work fine again.

It took a long time, and an armorers class at S&W to finally figure that one out.

Good luck with it.

Jim

[professor]

OK, I found and fixed some problems, but it's still not perfect.

I took off the sideplate and checked out what was going on with the hammer striking the firing pin. The major thing was that I wasn't getting sufficient firing pin penetration. This model 686-6 has the firing pin in the frame, and the hammer face was stopping short off the possible full travel. The angled ramp of the hammer would hit the matching frame surface before the face of the hammer, so the firing pin was not extending under power for the 0.04 to 0.05 inch it was supposed to. I couldn't see this from looking at the penetration as the tip of the firing pin came through the blast shield while dry firing. That was possibly because the momentum of the firing pin would let it fly further out of the blast shield against the counteraction of the firing pin spring when there was nothing to hit, but it didn't always have the energy necessary to set off the primer. I guess the proof of this was that a second hit on the light primer shells was unable to fire them. After filing the angled ramp back, I got the hammer face and ramp to hit simultaneously. That got me more penetration and eliminated the problem during testing at the range. I may still be a candidate for that Cylinder & Slide extended firing pin.

Endshake and headspace checked out OK. Cylinder is machined true at front and back, so the gaps to forcing cone and blast shield are consistent for all chambers.

While having everything open, I stoned the trigger and hammer, and removed the hammer spur as described in Pat Sweeney's book. I also took care of the trigger lock, removing the little spring and the "locked" plate.

After doing this, I did some dry firing with the mainspring screw backed out 1-1/2 turns (as it had been while experiencing the light strike problems). What I noted then was that the butt end of the mainspring would gradually slide toward the end of the slot, to the point where it started protruding out the side of the handle casting. With the Pachmayr grips I'm using, that means part of the spring will gradually start rubbing against the inside of the grips. And that could increase friction that could reduce hammer impact force.

For this past Sunday's match, I screwed in the strain screw all the way (8.7 # pull) to keep this from happening. What do you think about grinding a slight depression in the center of the mainspring so that it doesn't wander off the strain screw? What about replacing it with another spring kit?

Trigger is nice and smooth, though. I still had one light strike this match, which is the the reason for wanting to put in the extended firing pin.

Aerosigns, the way you described your heat problem, it sounded as though the crane would swell slightly and start binding, which would make the last shot(s) difficult. What did you end up doing, polish the crane pin down to give a skoosh more clearance when it heated up?

I'm thinking I might still be having a heat problem with the firing pin binding in the hole of the blast shield or in the firing pin channel.

[Round_Gun_Shooter]

Polish the firing pin. Chuck the small end into the Dremel tool and use Jewelers Rouge to polish the larger portion. It makes a difference.

Grinding the face of the main soring will weaken it. Try making the end of the strain screw truer so it can not pus off one side or the other. Also, rather than backing the screw out, shorten it.

Regards,

[professor]

Polish the firing pin. Chuck the small end into the Dremel tool and use Jewelers Rouge to polish the larger portion. It makes a difference.

Grinding the face of the main soring will weaken it. Try making the end of the strain screw truer so it can not pus off one side or the other. Also, rather than backing the screw out, shorten it.

Regards,

Thanks, RGS, polishing the fat end of firing pin sounds like the next logical step.

I didn't want to shorten the strain screw until I knew where it could be set and still get reliable hits. But the mainspring seemed to be "walking" toward one side as I would dryfire, and I don't know how truing the screw would help that. It was easy enough to have the spring centered with the screw to start, but each shot the spring would "hop" to the side a little, until it started protruding from the side of the frame. Why? I don't know. I wouldn't have noticed it if I hadn't had the grips off.

[revchuck]

I wouldn't have noticed it if I hadn't had the grips off.

Depending on the grips, it probably wouldn't be happening if the grips were on...

[AZGUNNER]

what do you guys think of the longer firing pin from cylinder and slide. Seems like 12 bucks well spent.

[Carmoney]

AZ, run a search here and you should be able to find my diatribe against the C&S pins.

Synopsis: I think they are 100% bad news.

Others feel differently, but I had too much bad luck for it to be just bad luck. If you know what I'm saying.

[AZGUNNER]

AZ, run a search here and you should be able to find my diatribe against the C&S pins.

Synopsis: I think they are 100% bad news.

Others feel differently, but I had too much bad luck for it to be just bad luck. If you know what I'm saying.

Thanks for the info.

[Round_Gun_Shooter]

To disagree with Mike a little is a good thing I guess I have had excellent luck with the extended firing pin in J, K, and N frame revolvers. One thing, I polish them before I install and test free movement with no spring. But I do that with the stock pins too.

Regards,

[Carmoney]

To disagree with Mike a little is a good thing I guess

Do so at your own peril!

[Round_Gun_Shooter]

To disagree with Mike a little is a good thing I guess

Do so at your own peril!

Sorry Mike, I'll never do it again Now, come take the horses head back,

Edited June 23, 2006 by Round_Gun_Shooter

[pskys2]

Round_Gun tell the forensics guys to look for minute pieces of a Dremel Rotary Cut Off Wheel. If they find it you've crossed Dr. Dremel!

AZ, I've used the C&S FP's and haven't had any trouble. Like Round_Gun I closely check the fit and then keep a spare.

Slight thread drift, Dr. Dremel's hammer on his 625 looks more like a whip than a hammer. There wasn't even enough metal left to drill "lightening" holes into! But, it did feel like an excellent action job.

[Carmoney]

I like the sound of that: The "Whip Hammer"--available this fall from the Rotary Gunsmithing Institute.

(The cut-down hammer on the 25-2 Sam shoots is now actually less than half of its original weight. I whittled away at that one from every conceivable direction. Jack Dremel sure would have been proud of what we've accomplished together....)

Now let's be honest, Dave--you felt the action on my 625 at Area 3 and the first thing you said was, "Kinda heavy, isn't it?" And that's what happens when you get spoiled by one of those Apex guns, your finger muscles get all flaccid.

[revchuck]

I like the sound of that: The "Whip Hammer"--available this fall from the Rotary Gunsmithing Institute.

"Whip it...whip it good!"