Fail to Fire, light primer strike

S

sparetime

Inactive
I have had a few instances with my S&W model 66 where the primer was struck too light and the round did not fire. I then backed the cylinder up and tried it again, the round went off the second time.

In looking at the end of the round,, the primer was definitely not as indented as the others that had worked fine. This has happened both with factory ammo and reloads. I'm using Winchester primers in the reloads.

What should I check before taking it to a gunsmith? I purchased the pistol used, so I have no idea if any work was done on the spring. The trigger pull in double action doesn't seem overly light, but I honestly don't have a lot of experience with double action revolvers.

Thanks for any insight.
 
There is a screw on the front side of the grip. It's called the strain screw. Essentially it tensions the main spring.

Make sure that that screw is tightened fully.

If it's not, what you're describing can happen.
 
Smith & Wessons "out of the box" rarely have this problem; and by rarely, I mean bordering on never. I have five S&W revolvers and in 30 years of shooting, have never had a light primer strike.

I also doubt you have a problem with Winchester primers (assuming a proper priming technique and seating depth). Although I prefer CCI primers, I've used thousands of Winchester primers (due to the shortages - we use what we can get) without fail. I rather like them, actually.

Primer seating depth is a possible cause, actually. Although I don't know how it would be specific to Winchester primers. If the primer is not seated deep enough, the first strike can push it in (and would have the appearance of being a weak strike), then the second strike will set if off.
 
"Smith & Wessons "out of the box" rarely have this problem"

Except that the OP specifically notes that he obtained this gun USED.

There's no telling what has, and has not, been done to this gun by previous owners.
 
Except that the OP specifically notes that he obtained this gun USED.

There's no telling what has, and has not, been done to this gun by previous owners.
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My point, exactly. (Now that I re-read my previous post, I can see that I worded it kinda funny - leaving an incorrect inference :p )
 
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The 617 I had a number of years ago suffered from light hammer strikes.
The only ammunition it was reliable with was American Eagle high velocity.

Everything else was very sporadic.

(It came right from S&W that way when I bought it new. It wasn't a case of the screw being turned out either.)

I agree though - first thing I'd check is the strain screw.
You might need a new one. People have been known to grind a thread or two off then run them tight.
 
As Mike indicated, the most likely reason is a strain screw that's not tightened fully. Since the gun was bought used, another possibility is that the previous owner tuned it by swapping in lighter springs and/or ground the tip of the strain screw (the latter a genuine case of "bubba-ing"). Any chance the previous owner used it in competition? Might've been tuned to be "Federal-only"; not uncommon for match revos.

Are the chambers and cylinder face clean? If the rounds aren't sitting such that their rims are firmly sitting on the cylinder face, the 1st strike may not ignite the primer.

There are a few other possibilities. In decreasing likelihood, they include (but aren't limited to) excessive endshake, internal friction, and an early DA trigger break:

When there's excessive endshake (fore & aft movement of the cylinder), the cylinder moves forward as the hand rotates the cylinder, and when the hammer hits the round. Endshake is easy to treat with Power Custom shims.

It's possible some internal friction is robbing the hammer of enough oomph to light off the round. The source of the friction could be a misaligned hammer rubbing the frame, or 2-piece rubber grips that're tightened enough to pinch the mainspring.

Do you experience light strikes in both double and single action? It's possible someone took too much material off the trigger/hammer interface, such that the DA trigger breaks a wee too early and doesn't have enough power when striking the primer.
 
Is it possible that the primers are set just a hair too low in the hole? I would think that this condition would cause failure to fire problems.
 
Ah. You were advocating for purchasing new.

How boring!
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Heh, yes I was. I have always purchased new.

But actually as of late, I've been looking around at used S&W revolvers. It does bring about . . . challenges . . . when scrutinizing them for potential purchase. Not boring - that's for sure :)
 
Some people back out the strain screw to lighten the DA trigger pull (which it will, to a degree). Its a poor choice, but some do it. The strain screw head should be flush with the grip frame, not sticking out.

If no other changes were done to the gun, the screw (flush) is the proper position and should give reliable ignition of all ammo. Tightening the screw really doesn't hurt anything (although it might increase the feel of DA trigger pull weight). You won't be able to tighten it much, anyway.

Some grips cover the screw (but leave enough room so it could be backed out..). The strain screw is the first (and easiest) thing to check if you are getting light strikes.

If tightening it cures your problem, great. If not, its time to see a gunsmith.
 
1. check the strain screw for tightness and make sure it has not been shortened.

2. Before going to a gunsmith, put a new mainspring in the gun (about $10 from Wolffe) as someone may have put in a lighter spring or done something to the original.

3. If those two things don't fix it, off to the gunsmith.
 
Same problem with my S&W 19-4. Tightened the screw as everyone has said and problem gone. CCI are the hardest primers followed by Winchester. Federal and Remington much softer. As noted, someone probably tried to lighten the trigger. Sometimes the screw becomes loose on its own. You may need some blue loctite if it happens again. This is an easy fix.
 
Before going to a gunsmith, put a new mainspring in the gun (about $10 from Wolffe)...
Click to expand...
Actually, if you're after a standard mainspring and strain screw, I recommend calling S&W customer service first. It's likely that they'll send you the parts free of charge; they've never charged me for any parts order that would have cost less than ~$20, and IIRC a mainspring is ~$10 and a strain screw is ~$3.
 
To be absolutely sure your primers are good to go, they should all be run through the intended gun at least once before hand. :p
This important and often over looked procedure will also prevent accidental discharges.
 
......possible that the primers are set just a hair too low in the hole?
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Or not fully seated. Primers not fully seated move forward when struck. Ditto if there is a headspace problem an the round move forward when struck..
 
I think the probability of the issue being primers set too high is pretty nil given that this was happening with BOTH factory and reloaded ammo.
 
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