Light strikes with new 66-8 revolver.

[JMR]

I bought a new 66-8 and have put a total of 500 rounds through it so far.
I've shot 50 Remington 357 125gr and 200 of 38 spl 130 gr without issue but when shooting 200 of Winchester 130gr 38 spl I am getting periodic light strikes (12 so far in 200 rounds of Winchester 130 gr). This is when firing in DA otherwise SA is 100% reliable. They have all gone off on the 2nd DA strike.

I removed the grip to check the mainspring and the strain screw looks like it was filed down from the factory. Checkout the pic and see if the strain screw looks altered to you. In the meantime I order a new strain screw from Midway for $1.99. If that doesn't fix it back to S&W it goes.

Seems odd for a new revolver to do this I had a 67-5 and put 3,800 rounds of all brands without issue.

 

[muddocktor]

I bought a 627 Pro a month or so ago and was having light strike problems in double action with it too on my reloads using CCI 550 primers. I ended up changing the mainspring from the stock S&W spring to the regular strength Wolff mainspring I had ordered a year ago for another pistol that I never used. The Wolff mainspring solved my problems and in conjunction with changing the rebound slide spring to a 13 lb Wolff it lightened up both single action and double action trigger pull with full reliability on lighting off rounds in double action.

 

[JAREDSHS]

JMR----I am certainly not an expert in any way, BUT the photo of your strain screw clearly screams either abnormal wear or something not right about it for it to be a new gun. You are on the right track. If it had been my gun I would have let S&W see it and fix it on their dime.

 

[oldgranddad]

JMR----I am certainly not an expert in any way, BUT the photo of your strain screw clearly screams either abnormal wear or something not right about it for it to be a new gun. You are on the right track. If it had been my gun I would have let S&W see it and fix it on their dime.

In the interest of education, what do you see in that photo that screams abnormal wear?
Thanks

 

[JMR]

Oldgranddad take a look at the tip of that strain screw it looks like it was filed flat and it's a new revolver.
I ordered a factory k frame round butt strain screw from Midwayusa and it's suppose to be delivered tonight I'll take a pic of it for comparison.
For a 1.99 screw I can handle that but if the problem persist then off to S&W it goes.

 

[JMR]

I got the replacement factory strain screw from Midwayusa which is S&W part #515288
and it measures 1/2" overall the strain screw that came in my new 66-8 is 7/16" long.
I have no idea how that got in there but after installing the longer screw the trigger pull is heavier and the mainspring is arched allot more.

The arch of the mainspring now contacts the factory grips where the plastic boss is cast to support the grip screw. I had to file the side of the plastic boss where the plastic boss contacts the mainspring. I really think S&W shortened the strain screw so that the grips didn't interfere with the arch of the mainspring.

I'll try is out on the Winchester white box but given how much heavier the hammer feels there shouldn't be a problem.

 

[WR Moore]

It does sound like you found the root cause. However, you should be aware than light strikes in DA can be caused by operator error. This happens when the trigger finger quits moving (or relaxes a bit) when the hammer starts to fall. This can cause the rebound slide to touch the hammer just enough to rob velocity and cause the misfire. The trigger digit needs to continue the trigger stroke once the hammer starts to fall.

 

[andyo5]

There does not appear to be a normal amount of bend in the mainspring. The strain screw may have been shortened too much by someone. Switching ammo brands brings the hardness of the various primers into play. Double action is where the problem would appear first because in that mode the hammer is not carried as far back as in single action.

 

[JMR]

I pretty well blame the shotened strain screw because the DA trigger pull is much heavier like around 14 pounds. When the trigger has been dropped and the hammer is pulled back the tension is allot higher.

BTW what is the stock DA trigger pull for the newer K frames?

 

[S&WIowegan]

I'm quite confident the screw you bought from Midway comes from the same vendor S&W uses. I'm also pretty sure an assembler/fitter at S&W shortened your screw to facilitate the stock screw which is an inappropriate thing to do.

However, it seems clear the bigger problem is with WW ammo. If those loads go bang with a second hit, that indicates primers not seated deeply enough. This is stuff handloaders learn the hard way. If the other brands go bang reliably, Winchester ammo is the real culprit.

 

[JMR]

I put probably 2,000 of Winchester white box through my model 67-5 that I bought new in 2004 and it always went bang and in the 3,800 I shot through it never went click like this 66-8 did. I'm kicking myself for selling that 67-5 a few years back. lol

I found a pic another member posted of his new 66-8 with the grips off and you can tell my original strain screw was allot shorter based on the arch of his mainspring.

 

[JMR]

I did decide to file the replacement strain screw by 1/32" from 1/2" stock length. The 1/2" length was a nuckle buster with a horible trigger pull and the factory S&W screw was 7/16" long which was too light set off the Winchester USA box ammo consistantly in DA.

So I went to the range tonight with a 100 round box of Winchester USA and all 100 went bang without a hitch in DA doing both a fast pull and staging the trigger. Seems like you have to find the sweet spot for DA reliability and a decent pull so a 15/32" length for the strain screw is it. Too bad S&W didn't make it this way from the start.