UPSET with my S & W 66-7, wont go BANG all the time.

[dhoomonyou]

I have a 66-7.
Went to the range today with an asssortment of 38spl & 357 Magnum rounds, made by Magtech, Winchester, Remington.
All ammo was purchased new within the last year.

The gun failed to fire about 6% of this ammo on the first strike.

I marked the offending cylinder's with a Sharpie. There were two of them. I will call them "one and four o'clock".

The primers had what looked like full size and centered primer hits and did not ignite the first time and sometimes the second time through.

From testing the gun with the "revolver checkout" gotten from another post, the 66 seems to be ok.

I wont be able to get it to a gun smith until next week.
I might contact S & W and see what they say.

ANY ideas??

thanks in advance.

 

[Chief 101]

I'm not familiar with all the S&W revolvers but I would only guess that the hammer spring is too light. There might be an adjustment. Someone with more knowledge than me will have better info so don't take this to the bank yet. Chief

 

[Stainz]

Remove the grips and try turning the screw on the front of the grip frame CW, thus tightening it. If it was loose, you probably fixed your problem. This screw secures and pre-loads the hammer leaf spring... it is NOT an adjustment, although some folks treat it as such. If loosened, it has a propensity to further loosen itself, reducing the primer strike while lowering the DA trigger pull. While you have the the grips off, look at said hammer leaf spring... it is secured by that screw... if it was bought used, and has a rounded central rib running the length of the flat, it is likely a Wolff reduced power spring. Sometimes they won't pop everyone's primers - I use them on my 'fun' firearms, which I stoke with Federal primered fare, which are the easiest to lite-off. If that is the case, Federal ammo should work fine... or have your 'smith install an OEM unit - it'll pop anything!

Stainz

PS That 66-7 must be one of the last of the 4" 66's - with the two-piece, ie, like the new .460/.500's, barrel. I have a 6" 66-6 with The Lock... and a soft hammer spring... but I make it's ammo. Great revolver!

 

[dfariswheel]

Step #ONE is to check the strain screw in the lower front of the grip frame.

This is a screw that puts the correct tension on the mainspring, and if it works it's way loose or someone thinks it's a "trigger adjustment" screw and loosens it, you will get mis-fires.

The screw MUST be screwed in TIGHT, and kept tight at all times.

Step TWO, check the firing pin tip for a broken or deformed tip, and check for adequate firing pin protrusion.

 

[JNewell]

If all of the above yield no results, it is also possible that the mainspring has been replaced with a less-than-factory weight spring, which can cause light primer strikes and unreliable ignition. My money would be on the strain screw not being fully tight.

 

[bakert]

Another vote to check the strain screw first. My 66-2 that I bought from an individual was doing the same thing some years ago. Only took a bit to tighten it up and it's been 100% since with all ammo.

 

[dhoomonyou]

the screw was backed out about a QUARTER turn.

Wont get to range until next week.

I check it every 500 rounds, only had about 325 out of it this time.

 

[Brian Williams]

Put some loktite on the screw or nail polish.

 

[dhoomonyou]

Brian Williams
Moderator

Put some loktite on the screw or nail polish.

Thanks, what color Loctite?

 

[Jim K]

Just tightening the strain screw might not help. Some "gunsmiths" cut off the screw so it would go in flush but still lighten the spring tension.

If only two chambers are misfiring, you might check those chambers for dirt or grease that could cushion the round, and make sure the cartridges are fully seated.

Jim

 

[JNewell]

Loctite - blue only, nothing stronger. The nail polish suggestion is actually better IMO, but degrease before doing either.

 

[mete]

Firing pin protrusion should be about .060". Yes the strain spring !!